//They just don’t explain it very well..//
No they don't.
Most people who have a meal out in a pub or restaurant do not simply get up and leave as soon as they have finished their last mouthful. There's usually wine left to be consumed and a digestif may be ordered (which in my view is "part of the meal", as mentioned in the earlier legislation). In my case I wait in the pub until the next (infrequent) bus is due. If staff try to oust customers as soon as they have eaten their last mouthful there will be many arguments.
Whilst I don't necessarily agree with it, I understand the basis of the "drinks only with a substantial meal" edict. However, this latest announcement has been made by "a Downing Street source." In the earlier "Tier" legislation there was no mention of patrons having to leave as soon as they had finished eating. Quite honestly it is a ridiculous notion. To serve customers alcohol with a meal but then allow them to remain for some time afterwards ordering more booze would defeat the object of the legislation (which, IMHO, is pointless enough as it stands, but that's by the way). But to insist they leave as soon as they have finished eating is simply ridiculous. I imagine this "opinion" (for that's all it is) has been voiced by a spokesperson who has engaged mouth before brain. But how unusual is that in this entire fiasco?