Beacon code question

Took of from Point Lookout, MO (PLK) this afternoon, VFR to Dallas
Addison (ADS). Requested VFR advirsories from Razorback Approach, and
they gave me a squak code of 1070. Razorback said they could not receive
my transponder, could only track my primary target. Once I was
switched to Fort Worth center, they read my mode C just fine, and said
Razorback had an ARTS problem, and could not track beacon codes with a
third digit of 7. No further problems into Dallas.

Question: assuming Razorback knew this (which FWC said they did), why
did they give me this code that they knew they could not track?

Thanks,
Bruce Riggs