Something being possible to do isn't enough evidence for rational people to believe that it happened. From my perspective, it's possible that you're Iron Mike Tyson, or that you died after your last comment and this one was posted by the assassin who killed you.

You are right, it could be. The problem is that its the kind of thing that would be almost impossible to disprove if it were false. So you can always raise doubts about a supposed disproof.

But it'd be really easy to prove if it were true and noone has offered proof. And there've been plenty of people who've looked for such proof, afaict.

My default assumption in such cases is that it is likely false.

If this was more than an urban legend someone would be able to dig up a company with this name and some indication that McD was working with them.

It definitely happens.

There are at least two companies that have branded [..] Kosher Gelatin™. One of them makes gelatin that is considered non-kosher by all of the major kashrus agencies.

"Kosher Gelatin®", when in the ingredients, just means the product contains pork.