Heroic Archimonde P3 "we wait" strat

So there is a strat going around, where the first group that ports away, kills the add, but does not get back up.
instead they wait until Gr2 comes down. so both Gr1 AND gr2 can use the port to get back up. and Gr2 does not need to play the intended stuff, but just skips it.

now is this an okay strat or is it considered an exploit and one could risk a ban.

example of the strat: https://www.youtube.com/watch?v=JwK2gxCuTXk&feature=youtu.be&t=373

We called a GM and he told us that it work as intended.

All the best from here ^^