Not at all. I must admit I've never checked the exact measurements of his dildo, only taken the measurements presented in this and his thread as QFT. Whether he's 6.5" or 6.75" (as you mention a swelling on the shaft) - no idea.
Some will call it downplaying, some will call it cheating caused by pumping.
Again I couldn't care less. IMHO Shane has the best looking cock in porn and it's massive no matter the exact size.
There are both longer cocks and thicker cocks than Shane but honestly they are really extremely rare - in porn, here and in real life.
The importance of finally having a realistic size for one of the biggest cocks in porn is bringing some reason into the absurd claims here and in porn of foot long cocks etc. If only people would accept that having a 7.5*6.5" cock is both extremely big - and extremely rare.
If they could accept that, we might be able to convince people that having e.g. a 6*5" is also both big and rare. And still way above average...