Failure to enforce a trademark weaken's that trademark's protection.
In the case of dots, trapezoids, whatever - those things may have never been trademarked in the first place, so no, they are not protected, and if they were ever protected, certainly that protection is minimal now due to the fact that nobody has ever heard of anyone suing over it. Real-world example: Fender lost the rights to their body shapes years ago when they failed to litigate against copies in good time. So you can make a Strat copy on your own time without any issue. So could PRS, if they wanted to.
PRS' birds on the other hand are trademarked, so yes, it's a violation.
It's all pretty simply really. If you really want to build your own guitar there are tonnes of kits out there that don't step on anyone's IP.