I do not believe SQF mandates the distance. I haven't been dinged on it and I have been part of SQF for a loooong time.
It probably falls back on Risk Assessments.
Ditto. In above reply, I mentioned my first program where we did most of the checks internally and had a monthly visit from a PCO to check us out. We had the PCO write up recommended locations for tin cats and used their licensed, expert opinion to push back the few times an auditor tried to say we had too few on certain walls (normally walls with long straight runs and no exterior doors). We would back that up with good trend analysis showing there was no activity near those areas and generally the auditors would be satisfied with those two things to justify amount/placement of our traps. Rodent activity was minimal at this facility to begin with, though our pest control program did specify that additional traps should be placed if we noticed increases in activity (can't remember what threshold our PCO helped us put into that SOP).
We did require a tin cat no further than 3' away on each side from any exterior door (whether or not it was used or always locked), in-between each dock door, etc., all the commonsense locations.