Probably one of the most neutral answers would be... It is a handy starting point indicator to get you roughly and quickly to the level'ish position you are looking for!
Had the same problem on a John Deere 5420. I recommend draining the fluid out of the back near the PTO, and not the drain plug. It really flushes out of the 2" filter hole compared to the 1/2" drain plug. In other words the filter hole will actually flush it, and the drain hole will drain the...
Here is the CK2510 Quick Attach bucket with the reference Item# stickers. I believe after Jul 2016 is when they were first offered. I contacted 4-different dealers and literately three out of four didn't know about the QA option.