your description of the first groups choice is directly responsible for the intimidation you describe and that is inflicted on those who fall into the second type/group.
There's none so blind as those that refuse to see.
1. Some members of staff will always finish before other members of staff regardless of whether they start early or not. Using "doing the job properly" to arbitrarily decide who's a good guy and who isn't is such a flawed idea it borders on the ridiculous.
Nobody and I mean nobody does the job properly...not entirely properly. To set up this false construct and then call anyone who doesn't adhere to it an idiot is bullying in itself, it's practically fascistic.
2. Management should never be allowed to compare the performance of one member of staff against another and use this to bully and intimidate. That's it, that's what reps and decent union members should be concentrating on not taking pious positions based on their own idea of what doing the job properly actually means and then blaming others for the fact that they can't stand up for their colleagues.
When you come on here and bang on about how people starting early or skipping their breaks is costing jobs or stopping part-timers getting full-time jobs it creates division and it's based on a complete misunderstanding ( I'm being kind ) of how a resource plan works.
As has been said many times before you cannot take hours out of an office based on people starting early, people skipping breaks or even people finishing early.
It has to be based on work ( at present in the form of items/ gwh and hours available. What actually costs jobs and full-time contracts in delivery is a) a structural decline in indoor workload and b) the overtime culture and Royal Mail's reluctance to convert it to contracted hours.