It may be that Jet2 do not do a head count on board which should have picked this up. BA have not done it for years (which was a constant bone of contention for me) 'relying' instead on dispatch to 'OK' the paperwork/SOB rather than an actual headcount (normally OK to divide that by one)
. On the odd occasion when I asked for one (it can delay the perfect departure, of course
) a minor b0ll0cking for non-standard procedures ensued, with 'delay' allocated to 'Captain'.