Ice = cold = less flavour.
If you have cask strength whisky though, you should be adding a slight of water to it anyway. The main advantage of a Glencairn is if you have to endure a serious tasting by guideline, where you need to return to the glass three or four times over the hour, then again after it's been empty for a good while after. The shape will hold the nose, and legs by finger are measured off a Glencairn.
It's a wanky, drawn out clap trap if you ask me, but don't tell the SMWS - because they take it kind of seriously....!
Welcome back nuggetchops.