dude is undersized at the PF position period.
How many times do I have to point this out? There's a difference between being undersized, and being short. Millsap doesn't lack the size or strength to play the position, despite being 6'7". His height and size is only relevant if it hinders production and effectiveness, which it doesn't in his case. His body size and effort compensate for anything lacking in height.
That's like somebody being stupid enough to say they wouldn't want a prime Ben Wallace because he's too undersized to play the C position. If a player finds ways to produce instead of being a liability, then it doesn't matter.
Jazz fans:
"he can guard guys at the 4. He has a defensive toughness a lot of guys don't have."
"He is very efficient and rather consistent. He shoots over 54% from the floor, and many of those shots are 16 - 18 foot jumpers. He has great touch, is a solid finisher in traffic and very rarely takes a bad shot. The fact that he always plays hard gives him an advantage in that he is ready anytime his opponent lets up."
"There's times where [height liability is] the case, but as a general rule? No. He'd be better off playing with a true center, as opposed to Al, but Millsap's defensive issues are overstated. And on offense, size is rarely ever an issue for him. Dude just has a knack for getting the ball up around the basket."
Again, saying that Landry is undersized, so they don't want Millsap is essentially saying that Landry's struggles of being consistently productive because of his height are the same issues Millsap has, only
Millsap doesn't have issues being productive, as he's one of the most productive and efficient players at his position in the entire league.