Well, if we're going to do that.
Apple has shown that they'd willingly help themselves to your data, while protecting you from others accessing it. Who knows what Apple will do with it? For all we know, iCloud Drive is now E2EE because they've figured out a way to ingest metadata and other information about your file as they store them. I mean, we don't know for sure if it's encrypted before being stored or not. All we know is it is now encrypted if you turn it on and Apple has no access to it. But to say nothing of it before or after. (/tinfoil on)
I'm not a Microsoft apologist, but I don't think they'd need to lie: "No data is stored for any period of time."
Anytime they've done shitty things, they have more or less been caught.
> if they also share the text with third parties
Legally, they have to share whether this data is being shared with third parties. It's about all we can do these days - for all you know, HN is collecting data on your activity and selling it to third parties for extra $. (Unlikely, but if we're gonna put our tinfoil hats on... no one is beyond suspicion! /s)
In any event, I know what it's doing and I'm not under any illusions that this is a privacy issue. I only use it to write things that will end up in public spaces anyways (such as HN, or Reddit). Any of my more private type of writing is done with offline tools.