So true! I had lived in an area where allowable plastics were designated by recycle number category. Then I moved to an area where the number was ignored and the policy was only plastic bottles ie containers where the top is smaller than the rest. Huh? Made no sense to me!
I was able to inquire about this when I toured the facility. Turns out the recycled material travels down a series of conveyors for sorting. Blowers are used at some stages. Certain plastics like clamshell containers are so light weight that they blow at the same pressure as paper. This made the sorting of paper much less profitable hence the ban.
There are reasons for what each district accepts even when it seems counterintuitive!