The main thing that this thread has highlighted is the lack of clarity and consistency about taking pictures on stations. This is probably the biggest cause of confusion and lack of trust amongst enthusiasts and staff alike. Perhaps something along the lines of this should be implemented:
I quiet agree, but the issue is two way related. last time I went to sign in at a medium size station, the response I got from the shift manager was "Why the f*** are you asking me for? Who told you that you need to ask me? We have got better things to do that have train spotters tell us they are here? Do what ever you like" and another time at a different station "They have to make up stupid rules for everything, we don't care here, do what you like"
Broadly I have found that stations seem to fall into four categories (There are of course the odd exception to each of these categories)
1) Network Rail stations where the guidelines are rigorously enforced
2) Stations that expect enthusiasts, who see the guidelines as a pain in the behind and an interference to them going about there jobs
3) Medium sized stations who get occasional enthusiasts who just don't care about or see the need for the guidelines
4) Small or medium stations who very rarely get rail enthusiasts where you get the odd jobsworth railway employee who has never heard of the rules, and believes there to be a blanket ban, so when you inform people of what you are doing you wish you hadn't bothered
Given the different local attitudes towards the guidelines I'm not surprised you get a significant minority who believe its just not worth the hassle of informing people of your presence, then add to that the fact that you can not possibly abide by the guidelines if you are traveling by rail, as you arrive on the platform!!! (so you cant do the before you enter the platform thing) and are in the wrong before you even start in this there is an implication that they only apply when not holding a valid ticket, and no provision for flying stop photography where you are at a station for a short period of time whilst changing trains and you do not have the time to inform people of your presence sign in then sign out again before departing.
As someone who narrowly avoided two railway station bombings, when railway stations were being regularly bombed by the IRA, yet it was a free for all so far as railway enthusiasts were concerned, so for me the security argument for them just does not wash. Yet some of the idiots who post there exploits on Youtube of things ranging from complete and total stupidity to teenage tomfoolery do not help the situation.
It would be nice to have a full open consultation between rail enthusiasts, and a mix of rail industry staff to work together to come up with some consistent rules, that have a fair consistent approach and that are communicated in such a way that some of the refusers and the reluctant compilers will understand the requirement for such rules, and why there are there, which has never ever been communicated in any way (Other than very badly as because, or terrorism)
Having had my experiences of the rules I personally take a very suck it and see attitude based on where I am and will sometimes ask and sometimes not, and the only issues I have ever had are taking the quick shot between connections.
My personal opinion is that the guidelines as they stand are unworkable and have no buy in from anyone, personally I would prefer a return to platform tickets, or some form of ID card system / ID photography permit that if questioned you could just show and staff would understand, or if you misbehave or act dangerously have it removed, although the cost of administering this would most likely be prohibitive