If there's an issue in this prolonged back and forth, I think it's more with Lucid's marketing than with their technology.
You can certainly find EVs that get close to, meet, or even slightly exceed their EPA ratings in real-world highway driving, such as Porsche, Audi, and Mercedes, partly due to their decisions to use the 2-cycle EPA testing protocol instead of the 5-cycle protocol Lucid uses. These companies -- especially Porsche -- also have a history of deliberately understating other performance criteria, such as 0-60 times and power ratings. Their mantra seems to be under promise and over deliver.
However, marketing mantras aside, in terms of actual range the Air will keep you on the road for well over 100 miles more than any of those cars. I'd much rather have an Air that only delivers 350-400 miles against its 520-mile rating than a Porsche Taycan that delivers all 250 of its 250-mile rating.
Lucid knew that --whether they liked it or not -- their new car would instantly and universally be compared to the Tesla Model S. The fact is that Lucid's powertrain technology is significantly more efficient than Tesla's (or any other brand's). Between the larger battery pack and the more efficient powertrain, any Lucid Air version will deliver at least 100 more miles of real-world range than the closest Model S equivalent. (For example, on highway trips on the same road across the Florida Everglades in the same condition, our Model S Plaid realizes about 72-73% of its rated 348-mile range while our Air Dream P realizes about 78-79% of its rated 451-mile range.)
It would have been folly for Lucid to choose an EPA rating method that would have produced a lower range rating than the Model S. Much better to weather complaints about falling short of EPA ratings (as do most EVs) than to suffer the slings and arrows of being thought to have failed to better a Tesla's range which, no matter how strong the denials, you can be certain Peter Rawlinson was hellbent to do.