HS/PE4 The Details

I just wanted to clarify what should be going on in HS/PE4.
The course video and info doesn't give much away and trawling through the forums I've found some posts about what parts of the body should be in contact with the floor. i.e I've seen mention that knuckles shouldn't touch the floor, but the gymnast in the demo has knuckles on the floor.
Would someone be able to explain the exercise please. 

Thanks in advance and apologies if this information is out there somewhere, I just can't find it

Coach has stated unequivocally  that the intention is to have the knuckles hovering just above the floor. I had the same question re. the video; Coach clarified that the filmed version showed an initial bump, then a hover with a possible brush, but the weight is to be supported, not rested on the floor

That makes more sense, otherwise it just seems to be a passive stretch with a weighted bar.
I've also seen posts discussing PPT and pressing the lower back being in contact with the floor etc. Is this the case as well?

Yes Matt definitely.

Thank you Alessandro