No. He's not "having you on". Using steel wool to dull the sharp corners on the edges of the rifling grooves is not only a good idea but it is one of the safest ways to do the job.
The steel wool is no harder than the steel in the barrel so although it does dull up the sharp edges of the grooves, it doesn't remove much material. Using steel wool is also one of the faster, safe ways to do the job.
I've seen people talk about using valve grinding compound, silicone carbide sand paper and things like Scotch-Brite pads to "break in" a barrel which is another term for dulling up the sharp rifling edges.
All of these have extremely hard abrasives in/on them. Yes, they will dull up the sharp edges fast but because they are much harder than the barrel, they will also remove material from the bore.
Of course, if someone doesn't care if it takes 100 + shots to do the same job with patched balls then they should probably use that method because it is the safest way to do the job.
