Is it common to remove most of the previous buttons/attachments during final refinement?

Both options are common.  Obviously, if the doctor asked Invisalign to remove the old attachments when this second refinement was done, they will need to remove them from your teeth in order for the new trays to fit.  It's also common to simply add new attachments when a refinement is done.  It's also common to have a miscommunication between Invisalign and the doctor's office on whether or not to keep attachments or to remove existing attachments when new ones are added.Good Luck!

If your new refinement has "x" # of attachments on the first aligner, then your teeth must have the same # to function properly. I dont know if your provider was aware, or not. My strong feeling is that you should be treated by an orthodontist, rather then a generalist, and preferably a premiere provider elite

Yes, it is likely that you don't need so many attachments any more, and it's often the case that we remove all of them for a refinement and place new ones as needed.  It makes sense, most of the movement is done, now it's just a matter of some detailing.