Many people confuse competence and dedication.
A competent developer would be more likely to send a PR using the tool with zero friction than to dedicate a few additional hours of his life to create an account and figure out how to use some obscure.
A competent developer should be aware of the tools of the trade.
I'm not saying a competent developer should be proficient in using gerrit, but they should know that it isn't an obscure tool - it's a google-sponsored project handling millions of lines of code internally in google and externally. It's like calling golang an obscure language when all you ever did is java or typescript.
It’s silly to assume that someone isn’t competent just because you know about a tool that they don’t know about. The inverse is almost certainly also true.
Is there some kind of Google-centrism at work here? Most devs don’t work at Google or contribute to Google projects, so there is no reason for them to know anything about Gerrit.
You are making the same mistake of conflating competence and (lack of) dedication.
Most likely, dedication says little about competence, and vice versa. If you do not want to use the tools available to get something done and rather not do the task instead, what does that say about your competence?
I'm not in a position to know or judge this, but I could see how dedication could be a useful proxy for the expected quality a PR and the interaction that will go with it, which could be useful for popular open source projects. Not saying that's necessarily true, just that it's worth considering some maintainers might have anecdotal experiences along that line.