Yes, there are limited numbers of them floating around, with the exception of the G36s which weren't made before the cutoff date, IIRC. You are also free to buy "post cutoff" 3rd gens as well. Compliance is not your problem... just watch out for post-ban (assault weapons ban, 9/13/94 cutoff) magazines that hold more than 10 rounds... That definitely can be your problem.
Bear in mind that most MA FFLs with their brain screwed on and enabled can transfer in any 3rd gen glock made before 10/21/98. Most dealers use the date code embedded in the serial number as a guideline for this. If you are going to go this route keep this in mind... it can save you a lot of
money rather than buying one in state and paying a $100-200+ premium for one locally.