The issue of flap operation during a turn specifically relates to flap retraction which usually means an immediate turn after take-off is the worst case of a climb, low speed and low level.
I don't know what or where you fly, but nobody I know tries to retract flaps in "an immediate turn after take-off." In fact, the general rule in airline operations is NO turn until above 400' AGL!
Further, flap retraction after takeoff is done on a briefed schedule DURING ACCELERATION. If the pilot adheres to the flap retraction schedule, adequate stall and gust margin is available to 40+ deg of bank, even though the normal turn is at 25 deg bank and max allowed is 30 deg. There is nothing unsafe about retracting flaps in a turn, as long as the design parameters are met.