He didn't exactly give it the "it's a load of old cobblers" line but did hint that the Waca legend was much different from the modern day reality.
"Perhaps it has a longer history in terms of that (pace and bounce), which is part of the fairytale story that gets related every time there's a test in Perth.
"The practice wickets are a lot quicker than in the middle, so that will be good for the guys. I remember them being the quickest I batted on anywhere in the world.
"Get through them, if they're comfortable on them, then being out in the middle won't offer any challenges."
McMillan acknowledged being one-down in a series is nothing new for this squad - in the United Arab Emirates and England within the past year for starters - but believes their ability to rebound quickly points to character and desire to show they are better than the previous result would indicate.
"Generally they adjust very quickly to conditions and opposition. Sometimes in first tests we've been a bit slow to do that.
"But there's no doubt the guys will be better off for the time spent out in the middle. I think they will be more confident from a mental side.
"We've got a lot of smart cricketers in this side. They tend to work things out pretty quickly."
Seamer Tim Southee, assessing his sore back, had a light workout in the nets at the WACA today and came through comfortably. On a day where practice was optional, only Southee, who needed to, and Kane Williamson, who doesn't but rarely misses a chance to net, took up the opportunity.
It means today will be the only practice session between the tests for most of the squad. Neil Wagner and Mitchell McClenaghan had a bowling session at local club Melville on Tuesday.
Williamson is sure to be a focus for Australia after his 140/59 double in Brisbane.
"I didn't realise what a good player he is," Johnson said last night.
"He can play all of the shots. He looked good in defence and it is a really good challenge and I am really looking forward to playing him out here on a ground that I really enjoy bowling on and really test myself against him."