I'm pretty sure it isn't. One leg extended positions are legal with one brace. But on level two if you release someone, it appears they better be coming down into a cradle:
B. Top persons must receive primary support from a base.
Clarification: Anytime a top person is released by the bases during a pyramid transition, the top person must land in a
cradle or dismount to the performing surface and must follow the L2 dismount rules.
The way to get around this is the still be receiving "primary support" from a the back spot because the back spot can hold both of her feet. Similar to the level 2 "tick tock". Figure out how to execute that and I'd say its legal. Also, they'd have to be connected BEFORE the stunt is extended (on the way up). Our J2 got deductions for that last season.