More details from the article:
There are questions circulating in the aviation community whether the FAA will revisit every certification step done so far for the 777X and what it will look like in the future.
In the wake of the MAX crisis, LNA is told that the overarching question is whether these changes are extensive enough to prompt the FAA to require a new type certificate rather than certifying the X as a derivative.
If the FAA chooses the former, it could add a year or more to the certification process. Boeing sold the X to airlines on a delivery schedule based on an amended type certificate. A new type certificate not only delays the delivery schedule, but adds costs to the airline.
So Leeham/Hamilton himself is not questioning the derivative vs new type question, he is reporting "the aviation community" is, but is not citing anyone associated with Boeing or the FAA. In short it's a lot of conjecture. He points out Boeing's plans presume it will be certified as a derivative but provides no one willing to go on the record to say that this is not the way it will happen. Member BoeingGuy
told us the certification basis for 777x was already established as a derivative, but of course that too is just an anonymous internet source, and the MCAS tragedy may have caused that to change. Bottom line is we have a lot of sizzle but no bacon.