> It's understood that if someone holds the title 'Engineer', they went through a certification process from a regulated body, traditionally. You can see this for example in countries and per state. [0] [1] [2]

I think you're misinterpreting the intention of the title of "Professional Engineer". As far as I can tell, it's for accountability for public projects (buildings, power, etc.). It's not strictly limiting what job titles can have the word "engineer" in it.

Most engineers in the aerospace industry don't even take the FE exam. Would you refuse to call most aerospace engineers "engineers" then?