Well that I got no idea but how it is right now is that dispensaries ARE allowed--they are, Ann Arbor, Detroit, Flint and a handful of other cities allow them to remain open but if they really wanted to, they could be closed down--its not going to happen yet it could happen someday if the people there wanted to get rid of them.
If a bill past that said cities had the right to OK dispensaries, the cities would lose some control over them...they would, IMO. Once the cities said OK, then it be harder to later on say no, we changed our minds. Right now dispensaries are technically illegal, so it be easier to shut them down if the cities really wanted to.
Same with concentrates, some cities allow the dispensaries to sell them, a few don't. I know one dispensary that doesn't and its in mean Oakland county--in fact I'm surprised it remains open but its in Walled Lake and that city always has been the "outlaw" or "outcast" city long before MM happen.
Its about control and right now the cities have lots of control over the sale of MM.
Thats my gut feelings. If somebody does know just what the problems were with the bills, please let us know.