The "sus" stuff was that he dropped his viper wall at A, then went B before the round started. It is impossible to do that setup during regular buy phases. BUT this stuff being sus isn't true. Using tacs to make impossible setups is actually a thing in Champions. Nivera did it at least twice during the match vs Sentinels on Breeze. Even on the C9 vs VS match, at the same timeout, K1ng (VS's cypher) did something similar by placing one of his trips near B, then joining up with his teammates at A, up until the start of the round.

It is a common thing to do during tacs in champions IMO. On the same tac, for example, K1ng (VS' cypher) did the same by placing one of his tripwires near B, and then going A.