First i have noticed this with 1909 version of Windows 10 after i have installed Enablement Package update on one test 1903 PC. It should report 18363 build (like it does via winver), but it shows 18362.
Then i have noticed that it also reports wrong CU number after the dot. Now it shows .449 for both 1903 and 1909 machines, but they are already on .476.