OSHA, the governing body of the whistleblower protection plan, considers it the exercise of a right to inform about dangerous, hazardous, criminal or other activities. It is logical that this same right exists for employees in private enterprise.
While changes to employment law seem massive at first, there have many made throughout the 20th century that are accepted as commonplace now. The idea of "right" implies that, yes, the right should be applied to employees in the private sector. I agree with the implication: the right to whistleblow and the corollary right to be protected from reprisal or retaliation belong to private sector employees as surely as to government employees.
I predict it will come about fairly rapidly that this will be added to employer disclaimers. Perhaps the future disclaimer might say something like: "We do not discriminate based on whistleblower potential or past whistleblower activity." Since OSHA enacted its regulation, Congress has expanded it to cover other situations. Private sector employees will be next, I suspect.
The OSH Act prohibits employers from discriminating against their employees for exercising their rights under the OSH Act. These rights include filing an OSHA complaint, participating in an inspection [etc] ... Since passage of the OSH Act in 1970, Congress has expanded OSHA's whistleblower authority to protect workers from discrimination under twenty-one federal laws. [italics and bold added]