It is possible that Oracle holding the patent[1] to methods on enums is the blocker, rather than any technical restriction.
I don't think programmers often consult 20 year old "inventions", so it seems pretty obvious on its face that the supposed benefit of patents, that something is _only_ locked up for 20 years, is quite pointless in software.
Anyway, for loops are safe, unless the for loop is over the elements of a linked list. Then you need to wait until next year: https://patents.google.com/patent/US7028023B2
Patents really have a chilling effect, even if a particular one might not be enforceable.
Having said that this is the first time I ever heard of methods on enums being patented, what a ridiculous patent. It's a good thing then that C++ doesn't have methods, it has "member functions" :).
Also C++ allows user defined operators on enums, which feels somewhat adjacent.
In the case of MPEG the result is MPEG LA, a US company which you need to pay to implement certain important standards. In the case of JPEG the result was a little different, since only the improved Arithmetic Coding of JPEG was patented, people just don't implement the actual standard, they cut out the patented part, so all the world's JPEGs (well, mostly JFIF files, which are slightly different but we call them "JPEGs" anyway) are a little bigger than they need to be for no reason except patents.
So no, I don't buy that "ISO is also very averse of patents" in a sense that would restrict this unless you can show that's a new stance.