Why not? Why should the restrictions on the balls be so tight? What purpose does it actually serve? Is the game markedly better/more fair with balls in the range of 12.5 to 13.5 than it would be with balls in the range 10.5 to 15.5? If the inflation of the ball is vital to the integrity of the game why does the league put so little effort into keeping the balls “safe” from tampering after inspection?
If there’s something arbitrary here it’s the rule. A rule I’m sure will be seriously “massaged” over the next couple of years, much like how spygate led to the end of the stupid rule banning helmet radios from the defense. Of course they still have the stupid rule that each team can only have one radio helmet on the field at a time. Not all rules are written equally, some are just plain dumb. And the Pats are really good at finding those.
Ludicrous. Might as well allow each team to supply their own sized footballs as well.
After all, per you, "why should restrictions on the balls be so tight?"
Even refereed pee wee football games don't allow those little balls you see at times tossed into the stands by cheerleaders.