What this means is that for the moment, People wouldn’t actually be engaging in Steam Cloud Play through the Steam client.
Steam Cloud compatibility must be offered with games participating in this beta or they must have some sort of online save system to allow people to actually save with Steam Cloud Play.
The company announced its Steam Cloud Play beta on SteamWorks.
Instead, at the bottom of the FAQs about Steam Cloud Play, it noted, “We may add additional Steam Cloud Gaming services in the future.