Well, you already know that FA will not put an octagon barrel on a FG gun, and as Benny 123 has posted above, you can get a PG octagon with a FG finish for the appropriate upcharge.
I have owned a number of both FG and PG guns, in some cases for more than 20 years. I really do like the smooth FG finish, BUT one should be aware of the fact that like all matte finishes, if a gun acquires some scratches and dings with normal useage, they cannot easily be blended in with the FG finish. If one wants an as-new finish, the gun must be returned to be re-bead blasted.
On the other hand, it takes only a few seconds of CAREFUL use with a Scotchbrite maroon pad to blend scratches into the normal PG finish. I have done so numerous times to a number of guns.
Only each buyer can decide which way to go.