I saw crystal-clock stable delays and the 0.9 sec even accounts for the slightly different delay timing when track power is DC. So the watchdog should not be getting pre-maturely cut off. Since there are no published spec I am aware of on how often or how soon after applying power a PS engine must see a watchdog to stay silent, I figure the more often the better.
Presumably ChooChooPaul will clarify if his inquiry is because he is trouble-shooting a problem or was messing around under-the-hood.