I think it does happen consistently, but I'd call that normal behaviour. After all, a swipe is meant to turn the page, and I'm happy that a
small swipe in the desired direction is needed,
anywhere on the screen, in order to turn the page. This is helpful for "one-handed reading", because you can both hold the iPad and flip pages with one hand. Try that with a book made of paper -- it's either impossible or a lot less comfortable.
To select text, I prefer to use the right-hand text-selection marker, dragging it to wherever needed. Plus, there are those very helpful and innovative
+Word and
Extend buttons in Marvin. (Although the
Extend button currently doesn't work beyond the scope of a single sentence.)