This is an enormously exaggerated statement, bordering on entirely false. Yes, the company has done this from time to time, including on some current Model S/X models, but the vast, vast majority of Tesla cars sold (the 3/Y) almost always have a different sized battery pack in reality, not just in software (~50kwh or ~75kwh - there is genuinely ~1/3 less cells in the 50kwh cars almost always).
The Model S/X sell in very tiny volumes, relative to the 3/Y too. There absolutely is not the same pack in "all their cars". Even the type of cells used varies between model packs, typically 2170/4680 in the 3 or Y, 18650s in the S/X. I think there are even some BYD blade batteries in some European Y variants, but I'm not as familiar with the German or China made cars.