Well, the way that's stated is false. There are some jurisdictions that forbid the use of Romex for anything. Period. (Chicago is one example.) So EVERYTHING has to put in wires in conduit.My electrician stated for a 60 amp service he could not legally use Romex (NM-B)
Again, not really accurate, because no one is mentioning the wire gauge.He said that Service Entrance cable was rated for I believe 65 amps where Romex was only rated for 55 amps.
This is just about using a correct wire type AND GAUGE that meets the criteria for the circuit rating. 4 gauge Romex is thick stuff and has a rating of 70A. Of course it can be used for a 60A circuit.
For some reason, some people get really obsessed with 6 gauge only and then make incorrect blanket statements like "Romex isn't allowed." No, that's just too thin a version of Romex.