Review significance of IsZipDeployment for Flex in standby mode

Tracking the TODO introduced in:
https://github.com/Azure/azure-functions-host/pull/9970

At the time the fix was made, we were unsure whether it is signficant that this codepath returns "true" for flex even when called in standby mode. This behavior is likely benign. We should get more insight from placeholder logs once the fix is in place.

Start by reviewing the TODO introduced in pull request 9970 and the surrounding IsZipDeployment behavior. Then examine the placeholder logs mentioned in the issue once available to determine whether returning true for Flex in standby mode is significant. Done means the behavior's impact is understood and a clear follow-up decision is documented.

Written by the indexing model from the issue text.