The way I see it is this: heaps of people have clear issues with using x. Some it is stylistic, some it is syntax related, some it is for how it reads. It has been well established that it is not going to cause a parsing issue because an identifier followed by an identifier is not currently valid syntax.
If x is equally valid as of or by, but people just don't like x for even something as simple as stylistic reasons, that vote is valid enough to reject it.
Why is x superior to the alternatives?
So to flip it on its head, if the original pitch was to use by, and people were proposing x and because by just didn't look right, or was too often used as an identifier, but the original author just wanted by, and rejected using x because there was not valid syntactical reason to reject by, then we are just defaulting to the original pitch instead of deferring to the clear rejection of by (in the real world x).
I was equally shocked at this. It felt like a huge slap in the face to the clear majority that had issue with this. Again, I refer back to the likes that some of these posts are getting.
It's also interesting to me that the verbal reading of [5 x Int] is supposed(?) to be the word 'by', so why not just use the word by for its spelling?
Interestingly, the more I think of it, [5 by Int] really means [5 by 1 Units of Int]. So it makes sense that by or of could fill this role.