By the later era, it very much is...it's why we talk about thing like Cage era uniforms, or TOS era communicators...it's exactly the language used when discussing a historical period piece...because, simply by sheer weight of episodes, Trek is a period piece in oh so many ways. That's why we see the period dress of the movie era turn up in flashback, or the period clothes of TOS turn up in enterprise...ever so slightly higher quality than what we saw in the sixties, and presented in then current styles. The Kelvin universe is essentially steampunk TOS period drama from that perspective...an alternate history leading to anachronisms and differing tech, in an otherwise mostly familiar period milieu. It's an easy concept, and seems a useful one.
Its not period, its made up. The visual style changed in every way in 3 years of setting time, even the look of some races changed. Its not an historic era, its a made up universe.