The problem with prestige farming is that it is easily programmable for a bot, so any scenario where the behavior can be seen will possibly be punished. Imagine that if you do it manually you get 1k of xp per hour, a bot can get 24k a day.
A "Botable" behavior adds more factors, such as the sale of accounts with high prestige which eliminates the entire process where a real user plays real games to get there.
Either r1 or r3, that game was totally false and with no intention of competition .
As users we can say that it does not bother us (the truth is I go to casual waiting for someone committing suicide with a mission so I win faster) but I doubt that the company will allow it if they can avoid it.
The other thing I think is if it really is worth the time invested. isn't it easier to work and use the money for the same number of hours to buy things? Because it is sure that even the ugliest work pays more than farming exp in the game. If it's because of the golden edge, I don't know, getting to it by losing must be quite sad even if no one knows.
It is not something new, in HS some people do it to get an additional 100 gold a day, the bot plays like a chimpance but plays so many times that every so often it wins. Basically it does a "good" to the community by losing 19 out of 20 games, even so they are banned if Blizz finds them doing it.
It doesn't matter that you do it "manual" at the end since there is no difference with something programmed for a different purpose than the one the game proposes (win))
I would recommend that you do not risk the account for something so insignificant.