This has been a recurring issue for me, too.
When I open a forum thread using the WPCentral phone app, the first post on the first page is at the top, as expected. After scrolling to the bottom, I swipe to go to the next page. Rather than automatically jumping/starting at the top of the next page, the app remains at the bottom, forcing me to manually scroll to the top to read posts in order of posting. This occurs for each and every page past the first page. >:-(
Open thread...read all posts on first page from top to bottom...swipe to next page...MANUALLY SCROLL UP TO FIRST POST on the new page...read all posts on new page from top to bottom...swipe to next page...MANUALLY SCROLL UP TO FIRST POST on the new page...ad infinitum.
It would be really swell if the app would automatically start at the top of a new page.