I've only done this stretch a few times so I can't say what benefits it has, but from the feel of it, I thought I'd share.

My personal trainer had me do this, I'm not sure why because I've never mentioned anything about pelvic floor etc.

Get on all fours (knees and hands) with back straight and parallel to the floor.
Spread your knees until you feel a stretch in your inner thighs (for me this is just outside shoulder width, surprisingly).
Now rock backward toward your butt until you feel a stretch in your groin. For me this is just leaning back a few inches.

I feel this stretch right in my junk, not in the taint area as other stretches have felt, so might be useful.

While I'm here, I'm guessing the stretch in the inner thigh is good as well. I get that from butterfly stretches too, but I notice sometimes when edging that that prominent ligament thing of the inner thigh (adductor?) feels like it needs stretched. And oddly, right before cumming, sometimes I feel a warmth there.