You did, however what I dont understand is the statement there that users with and without a purchase will end up in the members group. If their purchase has expired, they don't then have a purchase.
There isnt really any way to do what you want to here if you are looking for members registering through different methods being added to different groups. That isnt a function of the software at present. Users can be 'moved' to groups on a scenario, such as purchasing, but if you have it set to move back on expiry, it will indeed move back to the initial group (members or whatever group they were in). If you have it not move back, they would alway then be in the group the purchase put them in.