Some of those are better examples than others. Someone who works as an accountant can probably call themselves an accountant--they just can't call themselves a CPA if they aren't one and may need a CPA to sign off on their work. A notary is someone with a stamp issued by the state. I'm not even sure what defines someone being a professor; they teach at a school of higher ed? There's certainly no legal requirement they have a PhD.
But to your broader point, there's various licensing/guilds--some of which is stricter than others. For the most part, engineering is pretty loose which the exception of branches that deal a lot with regulators in particular, like civil engineering.
But to your broader point, there's various licensing/guilds--some of which is stricter than others. For the most part, engineering is pretty loose which the exception of branches that deal a lot with regulators in particular, like civil engineering.