I think a boot would have to be made out of hard plastic not to pack out.
I mean the whole entire thing.
If a liner @ all forms to the contours of your foot, it has just packed out.
I'm a size 10 but I've been buying 1/2 size smaller, 9.5 boots for 20 years, I grabbed up the only pair of Burton Grails @ the ski swap for super cheap, but the only pair was a size 9.
They were way too tight, had them heat molded once, they were still too tight maybe 2 more days riding after that.
They are now super awesome. I absolutely love them.
I am not you though! I like a really tight boot, that's just my personal preference. That's why I always go 1/2 smaller, I just was worried a full size might be pushin' it too much.
Couldn't have been happier though, luckily.
I think boots pack out depending on how big the size of foot going in them, my boots have packed out a tonne, because I crammed a 10 in a 9.
If I bought a size 10 They would still pack out I'm sure, just not near as much as my 9's.
I also don't think packing out is a bad thing either, only when boots get sloppy & don't hold their rigidity.
I see packed out as form fitted, as long as the boot hasn't broke down in anyway. My boots are packed out, but I don't think that's bad thing.
If they fit perfect now, they will just get sloppier from that point on.
If a half size small is comfortable I think they will only get comfier.
If whatever doesn't kill you, only makes you stronger.
Then I am so close to immortality