This new dependency adds very little over the original xz and xz could have just used a simple PR.

I kind of like the incentives created by this competition. This "what if someone takes your software, adds one feature, and sells it" argument has been made many times and I think the answer is that you, as the original maintainer, are in the best position to add features and if you squander that position you deserve to lose.

Seriously imagine the consequences of this "eat or be eaten" approach. What it incentivizes is not feature development per se, but fragmentation for the sake of it. This in turn leads to less attentation toward maintaining the shared base of the fragmented forks, as it has been superseded with features X and Y in different, probably incompatible forks.