Originally, cars using the drop-off/pick-up area could end up crossing paths with vehicles trying to enter the short stay area. They'd either have to wait for a gap or drive over the raised bit of tarmac that passes for a roundabout to exit. So I get the reasoning for the reversal; trouble is, they've charged that area several times over the last five years, none of which seem to have really helped. Drivers just do what they want now. The newly fenced-off area has notices saying not to park in the old car park entrances and to keep the area free fr access. Of course, drivers have been waiting there today...
I don't think there's any enforcement at any time now, unless it's done through ANPR. Once their 20 minutes are up they leave and re-enter anyway. Twice in the past 12 months I've seen people on traffic duty. Even the taxis person seems to have gone. Ubers and other PHVs I think are supposed to use the multi-storey. Leeds is bad for clear signage, which is why I see people exiting the multi-storey and turning left to try and leave the station (you can't do that; if the gated car parks weren't there you'd end up on the track). Meanwhile, there's a surface car park going spare with the gates now closed behind the barriers.