Some warbirds did have auto-retracting flaps in real life and some didn't, like the P-38.
While it is a pet peeve of mine that the flaps auto-retract in the P-38 and when I first started, was the cause of many spin related deaths, I've learned to compensate with better throttle control. You can use your throttle to control the speed of your P-38L (it's not a PJ, that's something you sleep in) and control the auto-retracting of the flaps.
I also agree with you about the P-38L in AH being a lot better than the P-38J we had in AW. I laugh at those that whine about how P-38 in AH sucks compared to the P-38 from AW, but those are the kind of guys that never really knew how to fly the P-38 in AW to begin with and you'll see them trying to out flat turn a Spitfire on the deck in AH like how you could with the AW P-38. Most of those guys now fly N1K2 and La7s.
Ack-Ack