I'm pretty sure on the recent Terrace podcast they said that you could take 4 keepers, name 3 and replace one if they're injured. So, in effect, it doesn't really matter as if Gordon isn't named in the squad, he would still come in if Gunn drops out and may still be the first pick from the rest. I know it would be odd to leave him off the list and then promote him to first choice in the event of an injury but it might be a token gesture towards the two younger guys, on the assumption that Gunn stays fit.