If you bought a top of the range machine for windows 95 and put windows 98 on it, it would have been slow.
Unless you had done the backups of your data yourself and wiped the installation of the machine, you were screwed. This is the same situation for iOS.
https://www.overclockers.com/forums/archive/index.php/t-2889...
But regardless, this is not the point. The point is they misled people and let them think it was that the new OS was slow, but it was not! When you replaced the battery the phone became very noticeably faster.
A base install of Windows 98 was a hell of a lot slower than a base install of Windows 95. But that was mostly down to the IE4 integration. Once you installed IE4 on Win95 the two platforms were pretty similar.