DingHao,
I'm afraid you don't know much about Mosquitoes.
The Mosquito FB.Mk VI Series II that we have in AH is the fastest Mosquito Fighter-Bomber of the war. The fact that it entered service in mid-1943 is irrelevant to that. There are later, faster Mosquito bombers and night fighters, but no faster fighter bomber. Further, the Mosquito FB.Mk VI Series II made up roughly a third of the total Mosquito production. Just that one sub varient of the Mk VI totaled half of what all 35+ other marks totaled combined.
The vast majority of Mosquito stories out there involve the FB.Mk VI Series II. If guns are mentioned in the story all bomber and photo recon Mosquitoes can be eliminated and if bombs or rockets are mentioned too, then the night fighters can be eliminated.
In summary, no, they are not talking about a later Mosquito.
Another point, many times during WWII a Mosquito FB.VI outran a Bf109 or Fw190 at low level. Now I'm sure they weren't talking about Bf109G-10s / Bf109K-4s or Fw190D-9s but rather Bf109G-2s / Bf109G-6s and Fw190A-5s / Fw190A-8s. In AH the Mosquito will simply not outrun these aircraft.
Yet another point, the Mosquito was one of the most dtreamlined aircraft of WWII. The Mosquito's radiators were the most streamlined radiators of any aircraft in WWII (slightly edging the P-51 IIRC, though I may have them reversed) and like the P-51's radiators they actually produced thrust. Radiators are one of the biggest sources of drag on inline engined fighters. The two Merlin 25s that powered the Mosquito FB.Mk VI Series II each produced 1,625hp. The Mosquito FB.VI was also optimized for low altitude work. Now, compare that to the P-38L. It is of similar weight with engines of similar power. It was not known as one of the most streamlined fighter, its radiators in particular being performing poorly in drag tests. It was optimized for high altitude work. Despite all of this, in AH it is faster at sealevel. The Mosquito very slightly edges it for a short while above about 3,000ft, but then the P-38 takes the lead again.
If the P-38 was faster, why did we want Mosquitoes for PR work instead? In reality the Mosquito PR aircraft not only outperformed the F-5 (PR version of the P-38), but also had five times the range.
Range, that brings up yet another issue with the AH Mosquito. In reality the Mosquito FB.Mk VI had a range of about 1,200 miles on internal fuel and 1,800 miles with drop tanks. In AH the Spitfire Mk IX has greater range than the Mosquito does.