Ping on OSX ends up with DestinationNetworkUnreachable instead of expected TimedOut

## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1514464
Build error leg or test failing: System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success
Pull request: N/A

## Error Message

**DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK** otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": ["Expected: TimedOut", "Actual: DestinationNetworkUnreachable", "System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_"],
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```
Two tests are failing on osx
- System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success
- System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_EAP_Success

```
System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success [FAIL]
Assert.Equal() Failure
Expected: TimedOut
Actual: DestinationNetworkUnreachable
Stack Trace:
/_/src/libraries/System.Net.Ping/tests/FunctionalTests/PingTest.cs(764,0): at System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Core(Func`3 sendPing)
```

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1514464
**Error message validated:** `[Expected: TimedOut Actual: DestinationNetworkUnreachable System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_`]
**Result validation:** :x: Known issue did not match with the provided build.
**Validation performed at:** 7/21/2026 12:20:53 PM UTC

### Report

|Build|Repository|Test|Pull Request|
|---|---|---|---|
|[1595461](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1595461)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_EAP_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1595461&view=ms.vss-test-web.build-test-results-tab&runId=44051966&resultId=103855)||
|[1595474](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1595474)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1595474&view=ms.vss-test-web.build-test-results-tab&runId=44051026&resultId=104241)||
|[1592450](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592450)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592450&view=ms.vss-test-web.build-test-results-tab&runId=43960908&resultId=104241)||
|[1592463](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592463)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1592463&view=ms.vss-test-web.build-test-results-tab&runId=43960708&resultId=103852)||
|[1582901](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1582901)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1582901&view=ms.vss-test-web.build-test-results-tab&runId=43671860&resultId=103852)||
|[1582899](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1582899)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1582899&view=ms.vss-test-web.build-test-results-tab&runId=43670864&resultId=103852)||
|[1580614](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1580614)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.SendPingToExternalHostWithLowTtlTest](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1580614&view=ms.vss-test-web.build-test-results-tab&runId=43605444&resultId=103058)||
|[1580626](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1580626)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1580626&view=ms.vss-test-web.build-test-results-tab&runId=43605322&resultId=103877)||
|[1562095](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1562095)|dotnet/runtime|[System.Net.NetworkInformation.Tests.PingTest.Ping_TimedOut_Sync_Success](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1562095&view=ms.vss-test-web.build-test-results-tab&runId=43007202&resultId=102605)||
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|2|4|9|

Start with src/libraries/System.Net.Ping/tests/FunctionalTests/PingTest.cs around line 764 and inspect Ping_TimedOut_Sync_Success and Ping_TimedOut_EAP_Success. Use the linked build results to reproduce the macOS failures and compare the reported status. Done means both tests report TimedOut instead of DestinationNetworkUnreachable on macOS.

Written by the indexing model from the issue text.