That doesn't say much for the folk(s) at that auto body supply shop. They should have the same skills as the body shop guys. The only problem with going to a body shop is they may not wanna talk to you if you only want to buy a few ounces of paint and they may not be equipped to put it into a spray can for you. If they will mix some up, you could probably get a supply to put it in an aerosol can though.
No it really doesn't say a lot about them, but... I think part of the problem is that certain companies use "secret formulas",... which often comes down to a slightly tinted base (you'll see that with the high end house paints too that's why Ralph Lauren and Behr colors are so hard to match in a "regular" paint, like CIL or whatever). So if company A makes the original paint, and has say a yellow tinted base, and you go to company B to get the paint matched, and their paint has say a blue base, there's a good chance that they can match 85% or so of the colors, but anything leaning towards a yellow will more than likely not be matched exactly.
In my case, company C (the body shop) had a different brand of paint, that was likely closer to the original. Plus the guy that mixed my paint at the body shop had been doing it for probably as long as I've been alive. The "kid" at the body shop supply was closer to my age, perhaps a little younger.
Experience wins out every time. :)
The body shop I deal with is owned by a former neighbor. :) And I used to fix his computer. That gets me some perks, but there are some shops out there that are willing to do a few ounces.
I think I got 8 ounces (about 2/3 a spaghetti jar full), which once loaded into a paint gun will allow you to paint damn near a whole faired bike. (Or in my case, screw up a few times on 2 panels, and have touch up paint for life.)