Sounds like you have it figured out - perhaps they are for more refining and not for all out production type work where you are sanding down an entire car after painting it, etc..
That is where 3M, Norton, and those other guys, rule, in my experiences too..
I will always want to use any paper that says wet or dry and use it wet with lots of water running as much as possible..
We would take an old small diameter hose, rubber or vinyl, cut the metal end off of it, and turn it on at whatever really low flow you want and set it on the panel so it runs water on your work and constantly rinses it off...
I see people on TV auto shows sanding this whole car down, dry, and without a guide coat and wonder - how bad is that going to look when you are done and its painted???
Its like the "Best of Earl Sheib" Show or something..
On this show tonight, they sanded this Firebird down by hand, dry paper, no block, no guidecoat, and then painted it in a dirty garage, not even water on the floor, it was some kind of flat black and you could see every pass of paint lines all over the car when it was done....
Wow - I just dont know what to say...

Dan F