This is a very complicated issue open to various degrees of interpretation. The one thing I do know is that we have a "Successorship" article in our "pending contract" that mandates any transfer of ownership REQUIRES the new owner to accept the union AND the terms of the contract. So, any contract with a "Successorship" article makes "Burns" and any other NLRB definitions of "perfectly clear" irrelevant. When you have a "Successorship" article in your contract, the buyer MUST accept both the union and the terms of the contract.
In a non union shop, the company can do whatever it wants. We all remember that XPO shuttered 7 terminals after the acquisition. In a union shop, a "perfectly clear" buyer must accept the terms of the existing contract. I will agree with you that the latest NLRB decisions have narrowed the definition of "perfectly clear" and made it easier for buyers to set their own terms and conditions prior to bargaining with the union. However, (see below), even though they have the right to set their own terms and conditions, they are still required to recognize the union.
"In Ridgewood, the new employer acquired a nursing home with a unionized workplace. The Board held that Ridgewood discriminated against existing union employees by not hiring them for the sole purpose of avoiding its bargaining obligations with the existing union. Because Ridgewood would have retained a majority of union employees had they not discriminated against four employees, Ridgewood was a successor company. However, the Board also concluded that unless a successor company discriminates against "all or substantially all" union employees, the company retains the right to set initial terms and conditions prior to bargaining with the recognized union. As a result, even though Ridgewood discriminated against some employees, Ridgewood had no duty to bargain with the existing union before it unilaterally implemented terms and conditions."