The excerpt is right on the money, but it lacks an important tidbit or two. The engines for the Model 322 were the same V-1710-33, a.k.a. C-15 engines, as installed on the P-40s contracted just before the 322s. Once the France fell, the British accepted the French part of the 667 contracted, but the complete contract was changed: only a few dozens will be built with C-15 engines without turbos, the rest (524 A/C) will be completed with F-5R/L (= handed, or opposite rotation) engines, and turbos. Seems like the Lockheed guaranteed 400 mph at 15000 ft for non-turbo A/C, and 415 mph at 25000 ft for turboed ones?
Once the 322s started arriving to the UK, and were fight tested, RAF felt that manufacturer promised what it was been unable to deliver. Ie. no 400 mph; though it would be interesting if someone is able to bring the test reports to the daylight. So the intended costumer stalled the things, and USAF stepped in, purchasing all the fighters that were stacking up in Lockheed's backyard, and whatever is going to be produced. The non-turboed ones were used mostly for training, and the armament was reduced in many of those down to 2 HMGs and 2 LMGs, since, without turbos the A/C were nose-heavy.
The high price might also be the problem, the contract was signed much before LL was introduced.