I'm pretty sure it doesn't say exactly that, and if it does it's not phrased very well at all!
There is no way to stream on multiple devices at the same time on any subscription plan unfortunately.
There is an idea to change this here. Feel free to add Kudos and comment to show your support!
Although I don't support this workaround, theoretically you could do it by taking one or both of your devices Spotify into offline mode (Settings>Playback>Offline mode, and you need to sync the playlists you want to play), then playing them both, as at that point it can't connect to Spotify to say it's streaming.
This post was by Taylor - I do not work for Spotify! If this solved your issue - Mark it as a solution!If you like my post - Please add Kudos! || Spotify Profile - Taylor | Feel free to PM me - Here ||