How about two different planes departing to exactly the same destination at exactly the same time from two different terminals? That's how I missed my plane from Belgrade to Vienna. I have no other explanation but that they do it on purpose.
It's much simpler; the incoming plane takes pretty much any available gate, because they are all almost always full.
Getting the two flights to Vienna in the same spot might mean an hour of extra waiting on the tarmac for a gate to open up.
I don't think this is that uncommon, so I've only ever paid attention to airline and flight number. I would recommend everyone else do the same.
Beginning to get worried and with no-one to talk to in the construction site of an airport I discovered that I needed to rotate my phone and then the extra columns appeared on their website. Yes I had tried scrolling and zooming, but in portrait it wouldn't actually render outside of the visible width.