I took the NACHI test, got a 94 on it and I have never seen an oil furnace or a boiler. I am about $400 away from being a "certified" home inspector. It is not something I am going to do but I was curious.
I talk to those guys over on tyhe NACHI BB and there are some ECs who hang out there trying to beef up their skills but those are only the ones who participate in the training and want to learn. Some are really conscientious and want to do a good job.
I fear a scary number of HIs are just in that business because their old business failed. Florida is starting an HI licensing program but anyone working now will be grandfathered in. Right now, anyone with a $30 occupational license and a flashlight can be an HI, flashlight optional.
If you want to see what the result of that is, I could show you pictures of my kid's house and what the HI reported when they bought it.
Missed items, one room with zero receptacles, served with a romex extention cord punched through the wall
The only light in the under stairs storage space (with the romex cord and plug connected water heater) was a black rubber lamp holder connected to a romex poked through the wall to a receptacle box, no connector and connected to the lamp holder with flying wirenut splices. Unscrew the bulb to turn it off.
All that was fine with the HI but he did note the uneven pavers in the next door neighbor's patio.
He did notice the home made "light kit" in the ceiling fan (a lamp holder, fastened to the hole in the bell with the blank 1/8" pipe plug, pigtail wires through 2 drilled holes). He called it "missing trim".
It was after that when I decided I would find out what it takes to be an HI.