Leap second statement is confusing

At the time of writing, the documentation reads

> represents the number of seconds that have elapsed

and

> does not take leap seconds into account

I found this wording confusing. At first reading, I questioned whether the calculation treated leap seconds differently from absolute monotonic seconds, as it should. Based on cursory tests, I can see that calculations are correctly performed in the calendar domain (UTC), not the time domain (TAI). The best wording I have seen to date is this, by [Markus Kuhn](https://www.cl.cam.ac.uk/~mgk25/posix-clocks.html):

> The POSIX second count ignores inserted leap seconds (and does not even provide an encoding for them) and counts deleted leap seconds

In practice, unix time represents a UTC date and time as a set of fields packed into an integer value according to a formula set by POSIX. The companion definition of unix time as a measure of elapsed time cannot be reconciled with this formula; it is effectively a false correspondence rooted in history and is a common source of error. It appears that ToUnixTimeSeconds [uses the latter definition](https://referencesource.microsoft.com/#mscorlib/system/datetimeoffset.cs) and conforms because the DateTimeOffset.Ticks shares the same limitation regarding leap seconds. The documentation there is more clear:

> It does not include ticks that would be added by leap seconds.

(edited to fix blockquote)
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* ID: 265528c3-9318-aa3c-6c32-a6a2b2b2cedd
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* Content: [DateTimeOffset.ToUnixTimeSeconds Method (System)](https://docs.microsoft.com/en-us/dotnet/api/system.datetimeoffset.tounixtimeseconds?redirectedfrom=MSDN&view=netframework-4.7.2#System_DateTimeOffset_ToUnixTimeSeconds)
* Content Source: [xml/System/DateTimeOffset.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System/DateTimeOffset.xml)
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