To my mind engineer refers to over level 3 trained, be it mechanical, electrical, or any other, up to level 3 a technician, or tradesman over level 3 engineer. However what I was taught as an electrical engineer was completely different to as an electrician, as an engineer more down to design, and an electrician more hands on.
But as the frequency raises and we leave copper wires and move to wave guides, it does seem more like a pipe fitters job to an electrician.
But I have worked with a plumber, and there is no way I could have wiped the lead pipes like he did, that was skill, and same with pipe fitter worked with them, and seen how they ground the heavy wall pipe so it was lifted with the crane into position and fitted first time, again a skill I do not have, and as to heating and ventilation yes they do tend to call themselves engineers, but maybe that is the right many for some one who can design a heating system fitted in the summer which 3 months latter when switched on works without any further adjustment.
As to boilers, I now work with them, as a volunteer, and again I can see the skill, seen one engine where it was converted from coal to oil, and saw how it did not work, and converted back to coal fired, watched them testing the safety valves, and seen how dangerous live steam is.
So should the guy who works on the foot plate be called a stoker, fireman, engine driver, boiler man or engineer, it is not simply shoving coal, or opening the throttle, water will not compress, so get it wrong and we have a big bang, keeping water over the tubes on inclines, these are real boilers, not things that only warm the water. And the carriages are heated with steam on a total loss system, clearly one pipe system, no return of any sort.
So easier to call the fireman Samantha, as even calling her a fireman one gets into trouble, fire-woman and your saying she is not part of mankind, and by time she has finished the shift, to look at her not sure she is, clearly would not want to upset her.