Ah, I see. Sorry, the text was too long and I'm not dutch so it was hard to spot that for me too.
But I interpret that part differently. I think them saying that there's an ambiguous section about risks does not necessarily mean that the ambiguity is in the responsibility of those who choose to not implement the detection.. it could be the opposite: risks related to the detection mechanism, when a service has chosen to add it.
I think we would need to actually see the text of the proposal to see where is that vague expression used that she's referring to.
This one is p2p: https://github.com/schlagmichdoch/PairDrop (or just try it in https://pairdrop.net/ )
But that also means that you need to keep the page open while the other device downloads.
Another p2p alternative is using webtorrent: https://instant.io/