So are OSA lenses cut in their own labs only or can they be supplied to retail shops for their own cutting?
Osa is a lens manufacturer. They make lenses and sell them.
So labs buy the lenses. Some finished some semi finished.
Shops buy from labs.
So (consumers)no one orders Osa lenses. They place an order and if Osa specs matches what you want
like for example
1. you make a pair of glasses -2.00 1.56hmc a basic lenses
2.The shop decides whether your lenses come or they send the frame up
3.if example your frame gets sent to Kv. They may or may not use Osa lenses to grind into your glasses
3.1 the optical shop calls and places an order for the lenses and a pair of -2.00 1.56 hmc gets sent over ( I do not know of any joker who actually calls as asks" I want to order a pair of Osa lenses " most don't know or care where the lenses come from.
Cutting the lenses in house is rarely done for better standards. Most of the time it's to save costs. You pay a lab to cut your lenses or you buy a machine and learn to cut yourself.
On rare cases where the opticians actually does it for quality control.. This person is likely a very difficult person to work with.
Like the people you work with who insists their staples must face a certain direction for better gripping