I think this is an interesting topic. I've always seen CX bikes as race-specific, and gravel bikes were for long hours of endurance type riding. CX bikes have the most aggressive geometry possible (while still accommodating the UCI max 33mm tires) and are built as light as possible, with 1x drivetrains. Gravel bikes are heavier, more relaxed, lower and had either 2x or really big range 1x setups.
That said, it's been interesting to track what kind of bikes are being used at big gravel races It used to just be CX bikes becuase there was no such thing as a "gravel bike", then around 2016 Ted King won Dirty Kanza on a Cannondale Slate with a suspension fork. A true gravel bike.
In 2017 the men's winner was on a 3T Exploro, billed as an "aero gravel" bike.
Then, in 2018, both Kaitie Keough and Ted King won Dirty Kanza on CX race bikes.
This year, both Colin Strickland and Amity Rockwell won the race riding a gravel-race specific Allied Able bike. The Allied Able is marketed as having a short and aggressive wheelbase and 1x gearing, which sounds a lot like a CX bike.
The gravel bike segment has definitely evolved to include a large range of bikes and some of them seem to overlap with CX bikes. Bikes billed as CX seem to be narrowly focused on racing. It wouldn't surprise me to see manufacturers moving away from entry-level CX bikes (like the CAADX), and instead relying on some of their more all-around gravel bikes that can be occasionally raced in CX.