Just returning from extensive flying in row 18, I have the following observations:

1) On each flight, 4-6 passengers attempt the crossover.

2) Of these, at most 1 is an Y passenger (who usually gets the wrong side during boarding). They always apologize profusely.

3) The rest are J pax, both during boarding and in flight. They do not even make eye-contact, let alone say "excuse me".

Given this pattern of behavior, I suspect they are all SEs.

My toddler has now been primed to puke on demand, so I hope they are bringing extra clothes on board!