Of course recruiters search public information.
Learn to live with it.
If your outrage threshold is this low then you’re going to spent all your life in a state of outrage.
It’s nit even interesting let alone important.
Information in github, far from being surrounded by an invisible force field of integrity protection, is actually prime hunting territory for recruiters and any recruiter who doesn’t mine it probably needs to explain to their boss why they’re doing such a bad job.
The recruiter in question, far from being apologetic should have said “yes of course I got your email from GitHub so what?”
The guy recommends avoiding this recruiter. I recommend you use this recruiter as they clearly display basic competence at the task of recruiting.