I take it they then don't have any tests of their own to assure backwards compatibility? Maybe I've been spoiled by using Windows for 20 years but I feel that

I take it they then don't have any tests of their own to assure backwards compatibility? Maybe I've been spoiled by using Windows for 20 years but I feel that we should be able to expect better from vendors than this. That goes double if you're paying them, though it sounds in Salesforce's case as if they pay you, because I can't see any other way in which this arrangement would make sense.