It's attracting much more than P2P these days. I have first hand experience of it. Every. Single. Day. EDI is now a place where a lot of the long haul carriers send people to transit to other long haul services. The airport has a connection time of 1 hour. This is impossible as even if you give yourself 1 hour to connect from Int-Int you won't make it as by the time you clear border control the check in for your onward flight will be shut. You have no chance at all. I would imagine many of the people who book a transit flight through EDI don't even realise they need to que up to enter the UK even if they aren't even coming here. "run of the mill" passengers wouldn't be affected by this... why would they?
The system employed at MAN sounds the same as LGW and LHR...it works perfectly well in those two airports and I do sincerely hope EDI copies that. It most certainly is needed to remedy the current amateur set up they have.