Oh definitely some revisionism from the HST hipsters (I think I might stick to that term!). Back when I used the ECML an awful lot between Newcastle & York (GNER & Virgin XC days), I’d actively go for the IC225. If time was an issue and a HST bellowed up, I’d have a deflated feel precisely because of the way the dated interior made me feel when using the train.
I'd not say the Mk4 original interior was much to write about either (though their present interior is very nice indeed after VTEC replaced the problematic seat cushions GNER fitted). It was like an cheapo version of the WYPTE Class 158 interior - lots of grey and red, and fairly rubbish seats. I guess it all looked very futuristic, though.