Short:
Yes you can!
Longer:
Yes and I’m thinking that’s kinda how they want people to do - Because if you like the game you’ll likely want to keep playing it after a month… and you’ll likely talk about how cheap it was, which is PR for the service to pull others in… and you might’ve seen other games on Gamepass that interest you too, so then you might keep the subscription for a longer time… and others who listened to your earlier talk might do the same, then they talk too, and pull others in…
And off we go - snow ball effect!
Bonus, if you like the game and want the best mods you’ll likely want to play on Steam eventually since going by past experiences the Microsoft Store version won’t let you fiddle with files as much. So then they likely get a purchase too besides the subscription money and Gamepass PR and snowball effect trigger.
I’m going with the Steam version at once. I know I’ll keep playing the game but I don’t know if I’ll keep a Gamepass sub once I have to pay regular price. And I know I want unrestricted file access for modding.
I’ll probably try it on Xbox through Gamepass though, I want to see how bad 30fps actually is. And that’s a win for MS too since I’ll suddenly be in the player count PR even if I just played for 5 minutes and went - Bleh!