replace TCP timestamp
The JonDonym documentation states, "[...] TCP timestamps can be used for tracking [...]" and "The JonDonym mixes automatically replace your potentially insecure TCP packets by their own.".
Tor should probable do the same or state somewhere why they believe why it's not necessary.
,, Sorry, if this is a duplicate or elsewhere documented. Search term site:torproject.org TCP timestamp or similar didn't bring results.