I am no virgin to the AR 15, but I'm not a gunsmith either. I've operated/owned several, but just bought one for my son that has me wondering what's going on. Every rifle I've operated does not allow you to select the "safe" position unless the bolt is charged. I just bought an American Tactical Omni Hybrid rifle that allows the selector to go to "safe" even without the charging the bolt. Function test was fine, was wondering if the lower was designed this way or if there's something faulty, first time I've experienced this scenario. Thanks

There are a small handful of trigger systems (The KE Arms SLT-series being the first that comes to mind) that allows the selector to go to SAFE when the hammer is down (i.e. bolt is not charged), but those tend to be higher-end models.  I would definitely reach out to ATI and ask if it's supposed to do that, maybe have a gunsmith look at it too, just in case.

Omni Hybrid. oof.
https://www.americantactical.us/public/files/Manuals/OmniHybridMay2017.pdf
it's busted unless you have a really nice trigger in it. I'd ditch the hybrid if it's feasible. an Anderson stripped lower is better. and I hate Anderson stripped lowers.
TLDR: the gun is broken. return it for a refund and get an aluminum receiver AR instead if you can.