Not in most jurisdictions, you don't need a NICS for private sales between 2 parties. Only NFA licensed dealers, like gun stores, are required nationally to file a NICS.
Under Governor Murphy's recently passed gun transfer law, a person who is not a licensed retail dealer and sells or transfers, or receives or purchases, a handgun, must go through a licensed retail dealer.
Not in most jurisdictions, you don't need a NICS for private sales between 2 parties. Only NFA licensed dealers, like gun stores, are required nationally to file a NICS.
You're right that it's not all jurisdictions.