yes b5 is bad (opens the h1-a8 diagonal)
but ..Bd7 is only marginally better.

Over at Red Hot Pawn where the database only holds games played with a time control of days and week and months, (ie no blitz or rapid games) this position

click for larger view

...has been reach 2,399 times (this number will by now have risen.) one las has 224 victims with it.

I have sent out a warning and shown a couple of counter traps for Black.

https://www.redhotpawn.com/chess-bl...

But the most amazing thing is that Alekhine with white somehow neither knew about nor saw <6.Qf3> in this position:

Alekhine vs Gajdukevich, 1907

guys, 400 years ago people weren't recording games like they do now. Greco's "games" are preserved as lists of moves on a bunch of ppers, without any comments whatsoever as to when or where they were "played", or by whom.

most of his "games" to me seem just to him recording interesting opening traps and tricky variations, like i do in order to remember them. he probably has played this trap a few dozen times in his career, and the games probably all went on a few more irrelevant moves that weren't worth the paper (which was incredibly expensive back then).

and true, on patzer level, Black surely doesn't have to resign here -- he will be down a piece, sure, but White may just blunder their queen in the next few moves, so what :) on master level, however, being down a piece is a sure loss and indeed resignable.