The common usage (but not 100%) of the term "retirement" usually includes a separation of employment. Most qualified plans are created for the purpose of providing "retirement income".
Who says the ER will rehire him? If the ER says (in advance) it will rehire him, both could be participating in a fraud. The statute is quite clear that a plan may permit in-service distribution at NRD. Since the proposed transaction is clearly not NRD, it could strongly imply an intent to circumvent the law.
BTW, if this EE is an HCE, a discriminatory practice could magnify the problem.