This is spot on. I simply cannot see how they will ever get 24 tph through the core in the peaks. Go to St Pancras northbound platform around 17:30 and you'll understand what I mean. It's taking well over a minute to dispatch trains with the constant 'stand behind the yellow line' announcements before they will start dispatch.
The driver dispatches him/herself on the TL side so the safety messages and whistle blowing isn't connected. The trains should go on time when ahead of schedule, or as soon as is safe when late. The platform staff are there to assist but can't delay things.
Meanwhile there was an ADD activation on a train at Hatfield not so long ago.