I decided to make a new thread because the old one was getting really long. Here's what my local inspector said about how they consider smurf:
It is considered a form of conduit for physical protection of the exposed wiring. We generally will always accept this in a residential application; to have the romex covered is the key. Of course, there are always limitations, but if it is just to the receptacles and switches, water heater or furnace where the wires leave the wall cavity, it should be ok.
Surprisingly they accept it not on the grounds that unfinished basements aren't subject to damage, but on the grounds that "anything covering the romex" is enough protection.
Even so, I'm going to do any new work with EMT though. It does look more professional.
But this explains why my entire basement was done in smurf.
PS- Judging on what I read, do not assume
that your local inspector will be of the same opinion, if you come across this message in google results or something.