Trust me, one sniff would tell you if it was electrical or if it was rubber burning even after the fact.
I have seen starters fail due to oil leaking on them.
Doesn’t happen right away usually over the course of months or a couple of years, all depends on how large of a leak.
Also most times it is due to valve cover gaskets leaking.
I spoke with an experienced mechanic I know and he sternly said, “a new, properly inspected/installed/tested belt without defects would NEVER snap as a result of a short in the starter or anything locking up”.
As I said don’t know your specific vehicle.
I’ve never seen it myself, but that’s not to say some vehicles may have unique setups.
If I had to guess either they installed the wrong belt or over tensioned it.
I did not hear any noise prior to losing steering. I will search service info (any suggestions of sources)?
This is in contradiction to what you were told.
In almost all cases having a belt slide over a seized pulley, it will scream quite loud.
Much like when you hear a car screaming when first started with a loose belt.
As to service info…. Might try googling a factory service manual.
You might get lucky and find it free on line.