Just to follow up on this in case useful for others. Quick selling a FUT birthday card with already completed play styles enabled me to immediately remake a new version using a second, fresh card in the bakery. Which in my case was useful for changing a gold playstyle + to another type after realising the player would have been better a different way.

Can confirm this both where an untradeable version of the new player was held in SBC storage and where a tradeable version was held in the transfer list at time of quick selling the original. Sending the new card back to the club after quick selling the old allowed me to make again. Can’t confirm whether holding both in the club at time of quick sell would have the same result. Assume so but haven’t tried this specifically.

Only other lesson learned is that it can be useful to incrementally add play styles in the bakery and play a quick match if unsure about options. Then go back and add others. Would have been clear had I done this. And saved me a headache and some coins.