I’ve heard of people spamming readme commits to get their github graph green... I guess if an employer is tricked by something like this they are kinda asking for what they get.
I can’t understate the simplicity of doing it, and I’d be nervous about someone taking the other approach as indicative of their technical depth. Then again, they’re already spamming READMEs so it’s not as if it was a strong signal to start with.
I don't ever see that as a negative signal, but I do see it as a positive signal if I can just read your code, so if you write good code in public and you hide it, I can't find it.
Of course, whether you care is up to you, but if I find solid code there I'm going to recommend skipping technical evaluation if you're considering working with me.
It doesn't hide your work at all (commit frequency is an awful metric of valuable work, some people do a lot of "fix typo" commits).
Every employer worth working for will at least look at some actual code you've written, both in your own projects and in contributions to others.
And even then an in-person interview should be able to offset any github activity or lack thereof.