But when a pro player starts to do that, that will be the start of it on pub games and it's going to be just like normal thing since everyone is just following the pros and the metas they create.
I don't think ATF only do this on the pro scene. He is known as troll on pubs so maybe he already experimented that shit before he use it on Majors Finals. They have coach to watch there item build during the game so I doubt that Notail will allow it if ATF don't know the outcome of that newly build item to that particular hero.
Player on SEA is worst than that and they are also very good on thrash talk and blaming when lose with the crazy build.
I'm not tracking their pub games so yeah, there's a chance that he did it first on pubs and experimented it there and also possible on scrims that they've made against other teams.
A practice game.
It's really possible that he did it before but it's not shown through private practice games.