It depends. I'm a non-trad. I called my undergraduate college about a committee letter and they said I was out too long to write a meaningful one, so I just got individuals LOR from professors I took at a nearby commuter school for pre-reqs. No schools questioned the separate LORs and I had a good admissions cycle. As longs as the LORs are good, I don't think it makes too much of a difference, but it might be school dependent.