This page is our investigation of cross-play feature in game called PowerWash Simulator. We also want to mention that - we always put manual efforts to find the precise, valid, and what is more important official information about different game features without using AI.
Yes, PowerWash Simulator supports cross-play, but only partially, so only players on Xbox One, Xbox X|S, and PC (via Steam and the Xbox Store for Windows) can play together.
We weren't able to find the cross-play confirmation on the official website, and we didn't get a response from the developers via email, so we asked on the official PowerWash Simulator Reddit and received verification from a moderator. You can check the post here.

You can also see the cross-platform play label on the game's Steam page, which serves as additional proof of cross-play.

Games can have different cross-play combinations, for example the game can have cross-play between PC, Playstation 5, Xbox X|S, but not between old generations like: Xbox One, Playstation 4, PC. To avoid any misinterpretations, we group them into so called "cross-play variations".
Any store inside the cross-play variation have a cross-play only with a store in the SAME variation. We also want to notice, that we put into variation not platform, but store + platform. That is required because some games, for example, can have cross-play between a Playstation 5 and Steam, but not Playstation 5 and Epic Games.