Are these cheap 0.02mm/m Chinese level vials really accurate?

I was amazed to see “high precision” level vials sold in Aliexpress, rated with 0.02mm/m resolution (twice more sensitive than a Starrett master precision level). They are sold for about 13 bucks. Any experience with thoose?

I’m not a big fan of cheap tools, more out of curiosity.

Aviv.