As regards the pressing E on the gsm-r… I think all drivers know what I’m talking about.
As a Driver, I thought you were referring to the old CSR radios which had an 'EM' button.
However, the GSMR has different methods to contact the Signaller. 'Big Red' is for a REC call and has specific protocols attached to it. 'Old Yella' is for making 'Urgent' calls and you can still use the 'Point to Point' call and immediately state 'This in an Emergency Call' or even 'This is a Rail Dangerous Goods Emergency'
Pedantism or otherwise, I do believe that it is important to understand that none technically stop a train. Personally I've 'ignored one' and made the decision to stop at what I thought was a safe place (didn't use emergency), the next one I missed and got a call from the Signaller asking why I didn't stop (failed to receive the stop message). I know plenty of Drivers who don't use emergency to stop and will just bring their train to a stand normally.
When making an 'Emergency Call' It is important understand the distinctions between Red/Yellow buttons as you treat them differently. I think it's arguable if you need to understand what priority levels each have. I made an Urgent call a couple of weeks ago and it was a split second decision whether to use Red or Yellow; hindsight is a wonderful thing. I would make a different choice if faced with the same situation again.
You could argue that you place emergency protection to stop an oncoming train… well the protection stops nothing.
I had a Driver tell me the other day that when you explode a detonator and there is nobody there, you just continue.