Not any orientation – if you present a QR code ticket the wrong way around, or even just angled away from the plane the reader focuses on too much, it doesn't work.

Contactless tickets work both ways, and in addition to that usually have a larger, more forgiving "landing area". On top of that, they can usually read through a wallet (but that's more relevant to regular commuters, arguably; tourists and infrequent riders will likely have purchased the ticket just moments before using it).