How is the gravel bike used?
1x is great if a gravel bike is rolling thru mud frequently, ridden on singletrack a lot, and is subjected to overall worse riding conditions.
2x is great if a gravel bike is used as a road bike for gravel roads and sees occasional softer/wet road surfaces as well as occasional mud/debris.
If I were entering 15 endurance gravel races a year from February thru November, where surface conditions will vary greatly, then I could see myself at least considering 1x since I would likely encounter poor roads in many of the races.
As it is, I ride because I enjoy riding so I stick to decent weather. I dont go down a muddy torn up 2mi long Level B road because I dont need to. Ill wait until that thing is dry to ride it another time. So for my recreational gravel riding and 2-3 races each year, 2x is perfect. Its just a road bike that works better on unpaved surfaces.