Surely at any terminal station with platform entry control it is good practice for the despatch team on platform and/or train to look back and confirm that the platform is closed to late runners before concentrating on making sure that those already on the platform have safely boarded and then initiating door closing.
The last thing you need is the fittest member of a group of staggering inebriates to make a late dash and hold a door open for their ‘mates’.
Indeed. And this is precisely why closure of platforms at some locations prior to dispatch is a sensible and practical step that will be continuing.