Code Editor Autocomplete not fully working

I ain't 100% certain if this is a bug or somehow intentional but I plan to ask questions first to see if it was intentional or a bug.

I do have Java knowledge but not Minecraft modding knowledge. Like with Eclipse, there is a autocomplete to quickly write code, as well as see the methods that a class may have, with Javadocs.

Inside MCreator, the autocomplete works with some stuff but not everything. An example is when I autocomplete "System.out.println()". It autocompletes the "System" and "Out" methods but when I try to autocomplete the last method of "println()", it doesn't pop up anything for that.

I also tried to look at the autocompletion for "BlockState" and nothing shows. Which makes it harder.

How may I fix this? Or is this a bug where I should report to the Github Issue tracker?