I would agree with most of the replies here. It definitely falls under RACK. Is there a risk? Yes. It is a huge risk? Probably not with a knowledgeable Domme.

Note: BB while the balls are tied or restricted is a no no. They must be able to move or you risk rupture.

I think the grabbing and twisting that I have seen some less experienced Dommes do is far riskier. It can damage the spermatic cord. I have heard multiple stories of that.