The thing is, the labs people hated time wasters (like me) They used a simple test as an entry key to investing in helping you: if you claimed to be a programmer and said there was a problem they waited for you to proffer patches..
The gap between XEmacs and Emacs is noted in the xemacs website in all it's painful glory. It's got politics, it's got lawyers, but it's also got code style and complexity.
I did a package for homebrew via git and PR, and the CI cost to make it "fit" their expectations was a multi-day iterative nightmare. I can see how it would be a barrier to entry for a lot of people.
The other side, I have managed to get one-line fixes into the hands of competent coders. There are times they will simply accept it, apply it, and move on.
Early in my career (1984) I accepted community patches for a body of code I was employed to maintain and imperilled it's IPR. It was a big deal at the time. I didn't think patches to C being used by the community was going to wind up there. I was pretty sure the patch submitters didn't mean to go there either (by stealth I mean, they would have been delighted if the entire body of code was in the public domain) -This was when we swapped code by 1200bpi tape reels in the post.
I think "too risky to accept community patches" is an excuse rather than a real reason. They just didn't want the paperwork and hassle to adopt the code. But the negative effect I can totally believe. I would have been very de-motivated by this.