The problem is that they (have the ability to) continue to make those decisions afterwards. You could have "known" an iPhone could run Fortnite at the moment you bought it and then after you received it in the mail discovered that they had decided you were no longer allowed to do that.
You could then say "well I bought it knowing they had the ability to change anything at any time" but I'm not sure I agree that you can give informed consent to a blank check.