Since I don’t think anyone responded to this, I’ll chime in to point out that this isn’t actually true. This is the entire reason we recommend Arkenfox+Firefox instead of Librewolf: Arkenfox is a collection of modifications you make to your Firefox preferences, but you’re still using Firefox and you’re getting updates (security patches, etc.) directly from Mozilla. With Librewolf you’re waiting for those updates from Mozilla to be merged into Librewolf’s code and released by the Librewolf devs.
For this reason, I agree with @bayesian in that I also don’t really see why Librewolf would be preferable to Arkenfox, which seems to do much the same stuff without forking the project. Maybe we should highlight Arkenfox more on the page?