https://us.forums.blizzard.com/en/wo...owlands/638371
It takes about how the 9.0.1 is for character customization changes and such while 9.0.2 is for beta changes. 9.0.1 will definitely be prepatch and they do say 9.0.2 will launch shortly before Shadowlands. Which indicates possibly prepatch (though more likely as 9.0.1) and 9.0.2 will probably launch the week before expansion to finish rounding things out.