@Bold The thread is about Sarada vs Shinki fight during the chunnin exams not Gaara vs Sasuke and that fight was interrupted in the middle.
Bijuu fighting for you is control indeed when the bijuu just can't break free of the jin. And there's no proof that he can't stop the jutsu either but logically nobody especially someone like Gaara who wanted to live would cast a jutsu that they can't come out off. The whole idea is stupid to even imagine. My guess would be that the jutsu ends after a certain time and maybe the caster can even set how long the jutsu stays active.
@Bold
Gaara was restricted to bring it out even though he was pissed at being wounded he controlled it. Sasuke stopped nothing. And when Gaara did bring it out, it didn't take long for Sasuke to be lying down on the ground. Sasuke simply couldn't do a thing.
And Gaara didn't run away, the leaf's invasion started in the middle of their fight but if it hadn't and if Gaara was pushed then he'd have made a show of Sasuke in front of everyone. In that regard Sasuke was lucky lol.