It is definitely a marketing and brand placement decision... The EPA protocol allows automakers to add a "voluntary adjustment factor" on top of the standard adjustment factors determined by the 2-cycle or 5-cycle test. So, it looks like a lot of automakers choose to de-rate their EPA outcomes by 10% to 20%. This plays well in the court of public opinion when reviewers like OOS, C&D, MotorTrend, SoC, Consumer Reports, etc. are delighted to report their highway range tests that exceed the car's EPA range. On the other hand, it lowers the range they can brag about in their own marketing materials.
It looks like Lucid wants to focus its marketing on efficiency supremacy and high range, so it chooses not to de-rate (or de-rate very little) the range from its EPA testing. That enables Lucid to publish a higher range to brag about. But then the outside reviewers get much lower results in their highway range tests and they bash.