when checking info for “Can't earn achievements”, below “in this world if:” every single possible reason is showed, even the ones not applied.
In the image shown, the world creator (me) made it in the preview, there is no behaviour pack activated and it wasn't build from a template
It is not clear what specific information you think is “wrong”. As it says, if you use beta features, that will disable achievements.
It is also possible there are other reasons, so please provide steps to reproduce as mentioned in the instructions on the reporting page.