I think the point op is making is with ‘stones’ or ‘furlongs’ etc you need to already know what that unit represents to make sense of it.

With metric units, even the infrequently used increments can be reasoned out just from the name of the unit, as it’s a standard prefix in fixed multiples of 10, not a random number that must be learnt.

So they’re neither similar or exactly the same in principle really.