ahh ok I have been in touch with them about some work I wanted doing on an Alu frame...good to know!
I suspect if you have zero oxidisation on the frame the finish will be fine. You will only know this once the frame has been stripped.
Depending on the quality of the finish you want and the extent of any oxidisation based on my experience I wouldn't recommend you get them to deal with it. Instead to take a specialist before SPF apply the powder coat - though I have no idea who that would be. Based on their inability to remediate what to me looked like very trivial oxidisation I don't feel SPF are skilled in that area.
However with a single coat I think the finish would be fine. In fact another guys frame I saw at the time looked very good.
Also worth noting Ray is a very nice guy to deal with.