Oh it's okay, it's a single-player game, it's not that you need any server capacity for that. Other than download servers but it's Steam's problem, not publisher's.
They have a cross platform save sync service which has been disabled, but it sounds like that wasn't load related. I'm not sure how big the save games are but 700k people mashing the quick save button every 30 seconds probably adds up.
They are a pain. I'm 9 hours in and at 1/17GB in Steam Cloud. I've been going between my Mac and an ROG Ally and syncing saves takes upward of 3-4 minutes and sometimes just fails silently (loudly if you launch the game, but still fails). Steam is definitely not built for that, considering that piece of the user interface barely gives any feedback.