I'll try and investigate how to improve this, but I also noticed some issues myself recently ... I usually open links via mmb (open in new tab) by default so I noticed a bit late but even if the URL gets changed, they automatically re-append the timestamp if you click on youtube thumbnails with lmb.

And on a separate note, they also seem to aggressively re-generate the url with as much bs as possible, as when I mouse over a thumbnail repeatedly I can see the URL previewer on bottom left of my browser change between having &pp=.... and getting cleaned.