this may or may not be a good format/idea, but it is not certain its a thing that will be implemented, so dont confuse people by saying it is
it was with kind thoughts towards helping, but it does not help if the information is not right
It's an approved format in the WoW Esports scene, used by all tournament organizers, including Blizzard themselves. The logical assumption of nothing being mentioned, except the gear, enchants etc. has got to be with the intention of using generalized arena rules. If not, then it's poor documentation, because no one would have the sligthest idea what the format even is.
But if Suntosh is correct, the format is slightly altered with the same aspect in mind. The big part is counter-comp'ing, although not forcing the winning team to play same comp still means you could have to adjust to a whole new set of situations, even when attempting to counter-comp.
This is why endgame tournaments implemented the rule that the winning team HAS to play the same comp. It gives counter-comp'ing even more of an edge, because you've now seen a lot on how that team performs with x comp. If they are allowed to switch comp when they win (even if they have to declare their comp swap), then the losing team can still be caught off guard, because they haven't experienced them playing it (depending on the situation, people could have done research on teams, or seen them play it earlier in the tournament, but you get the general idea). This means teams can keep altering comps as well.
There are a few factors that goes into why this is slightly worse than what is generally used. Such as scenarios where one team wins the blind pick, they are now in the lead on the counter-aspect of the game, which is a HUGE aspect, considering what state the game is in.
Blind pick winning team:
>Win
>Pick rounded comp to not get hard-countered
>Win/lose
>pick counter-comp
Blind pick losing team:
>Lose
>Attempt counter-comp
>win/lose
>pick counter-comp
Logically speaking, whoever wins blind pick with the format Suntosh mentioned, has a greater chance of winning the series. And that's even with the aspect of the opposing team adapting. This means that RNG plays a huge factor, and RNG should be left to the game itself, it already has so much, and not effect the format.
It would also be 10 times worse if map is declared before locking in comps, because map picking is a huge deal too. And that's not mentioned anywhere either, so... That would give the winning team even more of an edge.