Not wanting H1b is fine and legal, because you can’t simply hire them. You need to file paperwork go prove that you can’t find the equivalent from local workforce. GC is weird, if they needed security clearance, but security clearance takes more than 3 weeks.
Some positions only require a public trust background investigation, which is technically not a security clearance but people do call it so. You do need to be a "US person", which non-immigrants with work authorization are.