Holtzauge
Airman 1st Class
This is correct as many times the manuals or listed stall speeds are for the plane in "landing configuration" with flaps and landing gear down. Possibly useful if you are comparing one to another plane that use the same flap type/system and use flaps of the same size. If they don't use similar flaps comparing land stall speed doesn't tell you much about stall speed in a high speed turn.
Sometimes you can find the stall speed with flaps and landing gear up which is much better but in some cases (like Ki 43 to Spitfire) it doesn't work as the Spitfire cannot use it's flaps in combat the Ki 43 famously can. However the Ki-43 does not use the landing position of the flap in combat. It extends the flap and lowers it about 8 degrees which is nowhere near the landing setting. Spitfire flap does very little for lift and is pretty much an airbrake to create drag and steepen the glide path.
Sometimes stall speed for both flaps up and flaps down is given: For the Spitfire Mk I in the June 1940 edition 1565A of the flight manual it says 69 mph flaps up and 63 mph flaps down (IAS). And yes, the straight and level stall speed does not say much about things like g-loaded sustained turn rate and which is why Clmax, wing area and wing span is a better way to compare turn performance. Regarding flaps, the RAE actually did a report for the Spitfire's turn performance in which they concluded as you say that it does create a lot of drag. But even so they also concluded that the split flap in landing configuration did improve turn performance (especially shorter radius) as well. But if the Ki 43 could drop combat flaps then that certainly must have been an asset.
Lists several stalling speeds and either does not say TAS when it is TAS or says ASI when it is ASI?Spitfire Mk I N.3171 Trials Report
Spitfire Performance Testing, wartime flight trials and reports of Spitfire aircraft. Spitfire Mk I data.www.spitfireperformance.com
In conjunction to the stall speeds given in that report (78 and 68 mph respectively for flaps up flaps down) the other numbers are IAS which makes sense since otherwise they would need to state stall speed with altitude. In addition, those values also highlight the unreliable nature of stall speed numbers since they are different than from the 1565A flight manual, maybe due to a different all-up weights and/or speed indicators being used.