Another benefit for Williams is Albon's 18"wheel/tire experience. Wasn't Williams the only team not having had a test with those? I could be mistaken though.
Either way, his feedback indeed will be worthwile. Marko also claimed that certain wins by Verstappen were achieved thanks to Albon's simulator work input. So Albon definately has benefit for the team he's working for.
Albon might get the RBR camp some vital experience from the Williams/Mercedes camp, but let's not forget that Williams/Mercedes ALSO are getting vital information from the RBR camp by Albon.
In the case of RBR and Williams having a joint venture in working on an engine that'll become a VAG engine - very much possible - this would be an interesting feature. Albon will have Merc experience, and Honda experience, and looking to a change in the F1 engine formula in the future this will certainly help that project. Also, his experience with the 2020 RedBull, the 2021 RedBull, and the 2022 Williams will also help for the 2023 Williams car and then also feed back to RBR. Albon will find himself suddenly being a very valuable man.