With a smooth balance wheel such as on a 1520

true and poised balance is not done by Rolex or any other watchmaker..That is one huge drawback with any curb pin balance.

I tested not to long ago one of my Tudor MC with a Valjeux 234 fast beat caliber at full and half wind. The amp drop was from 260 at full wind to 248 amp..Not a significant drop and the pins relation to the hairspring was not effected. Once you center a hair spring curb pin layout, the amplitude loss is from the mainspring uncoiling energy not from a properly set up balance,

Now your statement "If the pins are too far apart, there will be a rate loss with loss of amplitude" This loss would also be seen on the watch timer from a full wind as well. You are bring up a short coming of a ill property set up hair spring to curb pin distance to begin with. A properly centered balance to curb pin set up will yield a very little rate and amp loss ay half wind.

Arthur