2 Donks
I am not asserting that an Archer needs to be in utility configuration to do a stall per se , Flying Farmer raised that point and like you, I don't have an Archer POH here to cross check, - if you read my story, I was quite happy to demonstrate stalls in landing configuration and slow flying.
1 - Practically, I don't wish to do a full power stall in an Archer with a very rear c of g, simply because I am concerned about the risks of getting into a spin in an aircraft that isn't cleared for one (thus we are now test pilots) and where one close relative (G-BBLA PA28-140) was lost due to failure to recover from a spin in 1996.
2 - Legally, I don't know how the lawyers would argue the definition of a whip stall (from the FAR quoted by Sensible), but my guy wanted me to transition from a 100kt cruise into a full power climb and I guess that a smart legal beagle could make a case for that being a whip stall
But #2 is pedantry, #1 is my problem.
I've done departure stalls in C150/2s and have no problem with them (apart from an egg sized bruise from bashing my head against the side frame when the instructor demonstrated the first one and we got the mother and father of a wing drop.)
But in a rear loaded Archer I ain't going to do one and if the instructor won't sign me off that's his perrogative. Mine is to find another FBO and CFI. If he wants to look at departure stalls, that's fine, but then we go in a suitable aircraft, my preference would be a 152.