I created a new issue about this problem back in July, but it was marked as "Resolved" and as a Duplicate (MCPE-89700).
My Minecraft takes only 1.2GB, yet it still displays the message when I want to update/download something from Marketplace and when trying to create Mario Mash-up Pack, but not when creating new normal world and playing old worlds (except for existing Mario Mash-up Pack worlds, it just crashes or takes me back to menu with worlds). Weird.
Also appears on Switch, I have over 1 GB and can't download anything (tried Adventure Time Mash-up Pack, which takes 10 MB (according to Microsoft Store, because Marketplace doesn't show how much a thing takes space), but can't; shows me that I need 55 MB.), and I have latest version.
misterblue, sorry not ;(