Hm, I don't know, I guess == on datetimes means "is the same instant" to me.
But an API should never get into a place where your personal choices should matter and various incompatible interpretations potentially make sense to different people.
The fact that your intuition of "these two timestamps are equal" is "these two timestamps denotes the same instant" seems problematic when we know that the notions of timestamps and time are not in fact aligned (because, for example, of leap seconds).