There is some confusion here as to how to define finishing.
More expensive Patek Philippe models aren't generally finished to a higher standard than normal Patek Philippe models.
BUT! More expensive Patek Philippe models do have more components and more interior angles than normal models. Some normal models have 0, 1, or 2 interior angles. And for the more complex ones, the sky is the limit.
So it really depends on how you define finishing.
Basic Patek Philippe models do not have "basic finishing" as even less expensive models of Patek Philippe would technically qualify for the Geneva Seal. And there's nothing "basic" about the Geneva Seal requirements.
Patek Philippes above a certain price point are generally double assembled. But to say there are different levels of finish on a Patek Philippe is definitely NOT TRUE and HAS NOT BEEN TRUE for decades.
In the past, Patek Philippe used to sell movements in two to three grades.
They would sell a low grade, more industrial finishing, less hand finishing, basic adjustment, basic spring (as opposed to a Breguet overcool), etc.
A mid-grade, higher finishing, more decoration, some hand finishing, a better balance wheel with more adjustability, and a hairspring with more features (better materials, a bend in the spring, etc.).
And a high grade. This would be high finishing, all the decoration one would expect, maximum adjustability of the rate and amplitude (usually with a Swan Neck Spring), and the top metal for hair spring, etc.
This practice ended decades ago. And for many decades, Patek Philippe has almost exclusively been producing the top grade level of watch movements. Virtually all of Patek Philippe's mechanical movements would qualify for the technical requirements of the Geneva Seal with few exceptions.