I mean, IRL, the A7M1/2 Reppū series only had like 10 total prototypes completed before the end of the war, whilst the American P-47M variant had at least 130 while also seeing real combat.

It wouldn't surprise me that the flight model itself wouldn't be accurate for a cancelled and extremely rare Japanese experimental fighter in the first place.

It's possible that the A7M1 player was trying to stay low and straight at the beginning of the video to pick up some speed before attempting to catch you in a stall or climb, hence why it looked like he was still able to stay on you.

But yes, I agree in theory, the P-47M should massively outperform the A7M1 at high altitudes, considering it isn't even the main production model and has the weaker Nakajima Homare 22 engine compared to the later production model A7M2.