I thought the official forum answer was that it is your responsibility to be in the right place significantly before the train is due? (I've certainly been on the receiving end of that after commenting on being unable to board a train after assisting platform staff with an incident and having the door close in my face)
If the passenger is meant to be in the right place (but rely on announcements and not RTT or similar) then there should be a bit of a two way street to help enable passengers to do that
Yes, that position reflects the general approach* taken by the industry. The reason being that it benefits more passengers overall to ensure as many trains as possible depart on time, thereby minimising overall delay. This makes a lot more sense when you witness how delay can breed further delay as a train moves through the network.
If you miss a train due to a late connection, or perhaps due to a platforming error, that’s unfortunate, but the correct remedy is to have recourse to the (actually pretty generous) delay repay scheme, rather than expecting connections to be held.
The references to doors being “closed in peoples’ faces” will almost always be to situations where people have run up to a train during the dispatch process, rather than any intentional act on behalf of the train crew. There’s realistically nothing that can be done to stop people who appear out of nowhere and attempt to board once the close door button has been pushed. I’m sure we have all done it - I most certainly do it on a regular basis(!) - however I believe it’s technically a bylaw offence, and it does carry a risk of injury, and potentially worse if you end up being clobbered by a door and falling down the gap.
*there are exceptions to this, eg my TOC will hold connections for last long distance trains, and perhaps branches on the Cornish mainline etc. where holding connections makes sense. Generally that won’t apply to anywhere London/the South East.