It's perfectly cromulent to hyphenate words this way. Doing so causes them to become adjectives. For instance, you would say "fast-paced agenda," not "fast paced agenda," or "fast, paced agenda." The latter two have a different—and in this example, weird—meaning.

In this case, I think it's a poor style choice, because there are two verbs and an adjective being combined, but there's nothing 'incorrect' about doing so. It might be clearer to say "users who think they are technical," but fixing the mixed pluralization and incorrect use of "their" would go a long way on their own.

What you did there, it has been seen. :)

What? Hyphenated compound adjectives have been a standard feature of English for centuries:

https://www.grammarbook.com/punctuation/hyphens.asp

I suspect the trip-up was caused by mixing up their and they're.