Yeah but when it's dark and your following them you can't see the overwing exits to count them (which is how I tell the difference).
And I hope you realise some A319 have 2 Overwing exits
BA 319, BA 320, BA320. The clearance is after the second BA 320, but the a/c lines up after the first 320
I am not surprised at all... In poor weather, or night, or the other ac head on, very easy mistake to make.
The LHR article was interesting, and the point about similar types seems well made - do not rely on minor type differences - as someone sometime will get it wrong...