I severely doubt it. If anything, they should have recommended it to me when one of my scripts abused sql to the point they rebooted the server. it was a flaw in the 3rd party script and was calling in a sort of loop to read through 600 rows, over and over, to end up with 1 value. they fixed it by tagging a new index for me that made it read 1 row instead of 600, and it solved the script. most hosts would have shut me down and not offered an upgrade, others would have told me i neeeeeed to upgrade. DH ... fixed it. So in the end, they saved me some cash, saved the sql server, and saved my ass, all at once.
That would get them fired more then likely. they'd have to notify the customer. it wouldnt be lawful to sell them a product they didnt agree to purchase. they specify in the TOS they reserve the right to shut off your account for overusing resources, not upgrade you for it.
1 and 2 are moot. they couldnt cause a magical VPS purchase. the customer would have to signup for it. DH would say hey, look, we have a problem here with X or Y and need it to be fixed. Worst case, they shut down your account. As I said in response to 3, they need to notify you.
What seems likely is that he signed up for it, or clicked signup from the page, and it signed him up. If you go to the PS portion of the panel and hit enable, then set up the setting to get the price, then hit enter or click the i want it, you should be signed up. i would think there is another are you sure page behind it, but im not testing this theory.
The other option, he gave someone else access, pissed em off, or they got curious and had billing access because it wasnt removed from their privs, and they signed up.