Oh, the way I understood "exclusive deal" was that the deal is exclusively with Google alone, not that Google is the only option for the user (which has never been the case, you were always able to change the default).

This would mean the new non-exclusive deal for revenue sharing implies Mozilla can have deals with other search engines or services (eg. Bing, ddg, etc) and get paid for featuring their search in the selection, joining the group of "recommended" options alongside Google. Google cant contractually tie Mozilla to exclusively recommend/prefer/set-as-default Google alone.

but again, depending on what is interpreted by "prefer" and whether the browsers are actually forced to not set a default (even when they are not getting paid for it) this can be an important change or no change at all.