He didn't imply that he knew more than the costume department, he said that they may have purposely used clothing from a slightly later era for aesthetic value.
This, thank you. Obviously the art/production crew have more experience than I do, but I still have eyes, don't I? And thanks to google I have access to thousands of photos and videos from that era to back me up. It's not like I'm making this shit up.
Looking for examples of woman's wear from 1962, I get examples like this:
Wardrobe is something a show like Mad Men does very well. Even with attractive actresses (including X-Men's January Jones) they still put them in what today would look like unflattering clothing:
And it's true of the men as well. You're not going to see guys with long hair and sideburns if you search for early examples. Men and women took their fashion cues from celebrities, athletes, etc. Notice how today very few men wears fedoras? Well JFK is often attributed with being the first public male figure to not wear a fedora, and soon men stopped wearing them. Women would copy Jackie O's hairstyles, then the women's movement started, and Joan Baez and hippies, and all of that affected fashion. If you want to find examples that are closer to what the women and men in this movie are wearing, you have to look to later years from the decade. This goes back to Goziller's comment about ascetics. They want the story to be set in 1962, but they (Fox) don't want to use that out of style ascetic, so they opt for more of a Mod Squad, swinging 60's version, which they probably think looks more appealing. They want Jennifer Lawrence and Rose Byrne looking sexy and showing off their legs. It doesn't compromise the script, although in 1962, these characters would be considered sluts for showing that much leg (seriously!), and the guys would be mocked for having such long hair. Considering Mystique (I presume) is trying to pass herself off as normal, dressing out of the norm for the time probably isn't the best way to do it.
I just know that when the DVD comes out there will be one of those bullshit little extras, where the costume designer will talk about how painstaking it was to stay true to the era and make sure everything looks authentic. Which would be a joke.