If you couldn't use straight thread into a conduit body you couldn't use an EMT connector.
I agree jointing RMC is more like plumbing but everything else is a simple, compression, "nut and bolt" situation.
If I had a concern about the "chase nipple/LB" joint it would be that there wasn't a star washer in the joint ... but I have a hard time making a code case unless it was some obscure "paint" reference. A short piece of straight thread with a hard biting lock nut would make me feel better. I look for reasonable fault paths in raceways, even with a green wire. You don't want hot pipe. I know the code really only gets serious in service raceways and fire pumps.
