I missed that too as I built to the letter and sort of wondered and now I am on the front spar to where it says disassemble debur and prime if desired.
I think on page 08-03 line 4 of step 1 the word prime got left out before the if desired. It does have the scuffing of the powder coat we missed on the vertical stab but no prime, even in the 10-17 update.
In the area of paint and prime system compatibility I think we only want to do the inside part if desired unless you've already got the paint and prime system selected and aren't going to change your mind.