What was carried out on this flight (presumably Easyjet) is exactly the procedure at an airline I used to work for, it is probably a procedure (like many regs) that is set out by the CAA. I.e search the immediate area and confirm who's bags belongs to who.
I think the OP was letting his/her imagination run riot regarding the whole 'drugs in a distinctive red bag' scenario which could easily be done whilst the pax still travels, spends the weekend in Amsterdam, travels around Europe in the dead of night and culminating in them committing murder on the Orient Express. Hercule Poirot indeed.
It is important to remember that regardless of commercial pressure the vast majority of airlines want the operation to be safe and secure and the overwhelming majority of crew (flight and cabin) will not neglect safety and security to save a few minutes and certainly not to put their own safety in jeopardy.
A friend of mine works for another loco and by all accounts safety and security is always taken to the extreme, almost verging on being anal in his own opinion. So if it is a 'budget bash' then that is unfortunate.
On the subject of Manchester security, I was made to feel like a naughty schoolboy at the weekend for being in the departures lounge without my biometrics being taken. Flying LAX to IOM via LHR and MAN. My biometrics had been captured at LHR an hour earlier but the security guard at the entrance to the gate 14x corridor in T3 made me stand in the corner whilst he dealt with the rest of the queue and made out that I had done something wrong and somehow evaded security.
What did you expect him to do? Fall at your feet begging for forgiveness whilst deploying a pop up sofa and finger buffet whilst you waited?