Doras went into service in September of 1944, some sources say October (as above) but lets not split hairs. Close enough. Fall of 44.
Any "1943" or "January 44" info on the Dora being operational (squadron combat service) is flat out wrong, sorry. Any such dates would be for flown prototypes only. Apples and oranges. As an example the RAF had Spitfire Mk IXs flying well before July 1942, but that has nothing to do with its operational debut date, which is July 1942, not before, makes no difference what the factory at Castle Bromwhich made, or what expiramental type they were flying before that. The 1st P-51D flew in November 1943...again, thats all well and good, but has nothing to do with its intro date to combat squadrons.
...not that that matters because the Yak-9U is in there too and its the same timeframe (August 44 therebouts), give or take a month so fair is fair. Dora vs Yak-9U is a fine matchup, seems to make sense. I would maybe add the Hurricane II and the A-20 as lend lease types if they aren't in there already, just for variety.
I could see making bones about it if it was just the Yak-9T available, so as it is I dont see what the debate is over.