Main difference being, IMO, that Joseph had a better open floor handle, which Moyer lacks. Moyer has some versatility to his game, but I agree 100% with Iommi -- right now, neither he nor Brisset project as a 3.
I'm normally the guy who tells people not to get too hung up on positions, that sometimes our forwards can be combos who are interchangeable [like when Wes / Kris played together a lot, or CJ / Southerland in 2013]. Might see that with Moyer and Brisset down the road, but neither one of those guys has the game of a 3 coming in.