Errata for the Foundry VTT tables perhaps.
Just tested rolling a slash crit and the entry it returned was "Severed Ear" which was shown as a lethal attack.
It doesn't appear to be in the Players Guide, and there is no update in the Errata. Looks like an error in the tables in the VTT module to me.
Have corrected it on mine, but one to be aware of for the next release.