Agree with you – my AP-900 and AP-1200 counterweights do not squeak either – and they do have bronze bushings, I thought they all did over the years.
If they are a problem on some shafts, why not try waxing the shaft with Carnuba Car Wax or Nu Finish, etc.
We often get overly concerned about causing noise on a calm, dead quiet night in summer. Besides, noise like light, obeys the “inverse square rule” – the noise the neighbour actually hears, if he is at twice one’s distance from the scope in the backyard, is only 1/4 in intensity of what you might deem worrisome or personally objectionable. In all likelihood, his windows are probably closed, and his (or your outdoor) air conditioner compressor will muffle the noise from squeaky sliding counterweights, if any.