Whether or not it is extended depends on:
PvNode ? extended :
depth < 5 ? extended : not extended.
I suppose it is possible to get some non-pv cutoffs at depths 6 or higher which will fit into the window and not trigger a fail high/low, though I can't really think of any off the top of my head other than TT (and the TT is not accessed on game cycles
). But the search will never naturally decay out without another cutoff as any cycle less than depth 5 is extended. Most of these will hit the 3-fold cutoff fairly soon, though in some cases of course it is necessary to go all the way to the 50 move rule (the number of unique repeatable positions available is >= 25).
BTW, the entirety of the code is which accomplishes this is about 7 to 9 lines....