Proton is Valve's version of wine running inside a container specifically made for Steam, while Lutris is only using wine.
And the versions being used by Lutris and the version being used by Steam are not the exact same thing. If you use GloriousEggroll for example there is the proton-ge-custom repo for Proton, which is the one Steam uses, and the wine-ge-custom repo that Lutris uses.
I'm not even sure that the latest "GE-Proton8-14" and "Wine-GE-Proton8-14" are actually equivalent to each other. They were released two weeks apart and might be based on slightly different wine and/or dxvk versions since they are using whatever the bleeding edge git commits are, rather than actual stable releases (i.e. using commit #ABCD1234 instead of release version 1.2.3)