It doesn’t matter if it’s a toss or not, it’s illegal.
It is not a toss by definition, because it does not come from below prep level, even though they bend their legs.
However, a vertical release cannot land in a horizontal position unless it’s braced. Rule 3.5.5.c says that a release stunt transition has to be braced unless it’s a vertical release that lands back in a vertical skill or a horizontal release that can land in any non-inverted position. This isn’t one of those two exceptions, so it’s illegal.
In order to make it legal, they need a bracer, or someone has to remain in contact with the top person’s ankle/foot so that there’s no release, meaning they could go to the prone, but probably not do the ball up