Pectoral fin clips are rarely, or never used. I'm not aware of any hatcheries clipping pec fins in the last decade. If a major fin is to be clipped, it's almost always a pelvic fin.
BKK has similar experiences to myself. After having worked in hatcheries for the last 10 years, pectoral fin wear is common on hatchery fish, especially in circular containers. You'll often see dorsal wear as well. More and more hatcheries have been switching to circles, so this could become more common. Pectoral fin wear will also become more common if tanks are stocked with higher densities (ex hatcheries are asked to take on more fish), or if they have starve days (normally to control size if they are becoming too large too quickly, or before movements occur).
I can certain that any fins clipped results in smaller fish. Is this because they are simply hand fed at birth and don't learn the ability to hunt for a while ? Or is the adipose fin help for sleuthing reasons. I dont know a lot about this im hoping Ralph can step in here.
Why not a max clip only ? If the adipose fin help ? I dont know.
Max clips are also not used often due to being unreliable. They often mimic angler injuries where a max is ripped off. They can also grow back fairly easily if a part of it is missed, and they are pretty time consuming to do (and carry high risk of eye injury if you have inexperienced clippers). They also impact how fish are able to eat. Despite their issues, these are still used in some places, but less commonly now.