I never completely bought this line of reasoning. To start, why was it exclusively the M48 that suffered this problem? The premium German M47 remained at the same BR as it’s American counterpart all throughout this time, even being broadly similar to the M48 in overall attributes.
Additionally, it’s not like this lineup was particularly weak, between the Leopard 1, M48, BMP-1 and eventually the Marder 1. They also had arguably the best SPAA at this tier until the M35/55 was introduced, as well as arguably the second best CAS. Yeah, the British were stronger, but the Germans had what was widely considered to be one of the best 7.3 lineups in the game during this period.
We also never saw the inverse, American vehicles being dragged up well beyond where they should be on the backs of the supreme British lineup of doom. The American 6.7-7.7 lineups have been remarkably stable, with only the T92 being moved up (and somewhat recently, as I recall). Outside the big global decompression that happened a while back, that is., which from memory only hit the American M48 and M60. Not really a comparable shift to trying to put a tank 2 BR notches under it’s identical clone.
I have a theory that Gaijin only said that because the average German player was just straight up doing worse compared to the American one, and there was no way they could announce this without leading to a bunch of toxicity around “X main bad”. So they had to try and come up with an explanation that would satisfy. But there are other possible explanations.
One point Oxy brought up is the fact that it was relatively new, and therefore mostly being stock ground (with the infamously bad APCR stock grind). This would have tanked it’s stats even with all else being equal.
The other obvious explanation is a lack of player training. German players coming to the M48 would be mostly used to tanks like the Tiger, Panther and Tiger II, and would be relying on a punchy, damaging gun with solid armor to back it up. That’s how the game has effectively conditioned them to play.
Meanwhile, the analogues in the American tree would be the M26 and M46 (and possibly the M47 is players decide to grind it), tanks that play very similiarly to the M48. They even share practically the same gun. Even earlier tanks like the Shermans emphasize the hybrid brawling/flanking “jack of all trades” gameplay the M48 requires.
Simply put, the average American player will be much better prepared to use the M48 than the average German player, who’s experiencing an entirely different playstyle than they’ve been trained to use. Something that could be solved by better tutorialization. Or encouraging players to try multiple different lines, rather than “maining” one.