Boots always count, regardless of game type or outcome. This means practice games and VTEs still count to boot rate, making it possible to have a rate above 100%
It's also possible to achieve a boot rate above 100% by getting booted multiple times in your only game played. Essentially you set up the settings so boots turn into AI, while having taking over for the AI allowed for a very large number of times. You then also make it so that AI's don't surrender when only one human remains. After that, it's all about getting booted every turn without having your opponent finish you off(like doing it with an alt or a friend, or simply asking the opponent whether they want to help you with it).