Yes I noticed an imperfect fit
Had to replace a swivel caster myself for a machine I was giving away...I noticed the imperfect fit of the mounting plate too. Annoying to me...I like things to fit correctly. Perhaps a different brand fits better or Electrolux made them themselves or had a company make them for them slightly different than standard so if a new one was needed, an off the shelf item from a hardware store wouldn’t fit and people would then buy from Electrolux. Not quite sure. The swivel casters were started at least in 1953 and maybe this is how the base plates were then and so they just kept those specs all those years to not to have to stock more than one for all models that used the swivel caster.
Not all models use the swivel caster, most pre 1980 lower level models are not equipped with it as outlined above.
Jon
