I think he's just stating the facts as they stand. I don't think the track is electrified between Ore and Ashford, so it's a technical impossibility for electric trains to run along there. Similarly I doubt diesel and electric units can be coupled together. Attitude doesn't come into it. It's not a case of inflexibility on Southern's part.
Of course, whether this stretch should be electrified is another question...
I understand that these are the facts as they stand. My main gripe is that there is no will to change the standing. There is absolutely no way certain issues which people just shrug their shoulders over in this country would stand elsewhere. Absolutely no way. I cannot see the German's suggesting the reason for a short train is due to being unable to couple diesel and electric trains together...they'd have ripped up the track, installed electrics and got a swanky long train cruising its distance long before the stadium was built.
The Germans would not stand for engineering works every other weekend for however many decades on the only rail route into Brighton.