Stae, it's really good that you bring this up. I believe that I have seen this happen also, and to be honest, this is why I tend to err much more on the side of caution and when I see a chain getting to the 1/16 point, I am concerned that I will forget to check it more regularly and to avoid unneeded wear on the drivetrain, I'll just change the chain.
I figure it's not worth eeking out every last bit if inattention could mean more wear on teeth front and back---basically the traditional view t of why to change chains.

Re your observation, I certainly don't have clear evidence from taking time notes, but I think I've noticed this in the past and been surprised, especially from thinking it would be linear and projecting x kilometres into the future.

I wonder if others have noticed this and if anyone has actually kept notes.

Here's my theory, it's like trying to loosen let's say a pole stuck in the ground. You push and pull on it side to side, for a long time it doesn't loosen. Then you get a little play and it allows you to put more force pushing and pulling, the space widens and as it gets wider you cab fiorce it more and more.

Chain wear won't be the same, but I figure as the bits wear inside, it allows more grit to gather, which does a faster "sanding down" effect, which widens the space, more stuff gets in, etc.

This touches on why I like a thinner chain lube, as I feel it flushes out particulates when I apply it, which I see on my rag when I pass the rag under the chain after I do the one drop per joined section, I also always "turn" the rollers a bit to work the lube in, and to wipe off the extra.
Goes without saying t to wipe chain before applying, or you just transport all the crap down into the innards, just common sense.

Anyway, that's my theory supporting your observation.

Again, very good to bring it up.