Genuine question, why do people think the level system doesn't exist?

Hi, im an autisitc adult, been diagnosed for about 2 to 3 years now. I apologise if this isn't the right flair, they don't have one for questions specifically.

Its been a reoccurring thing for me with people, specifically online, where I mention the level system, which here in Australia is only really used for determining how much care you receive from the government, as far as im aware at least.

When i do mention it in passing, more than one person would respond with saying "the level system doesnt exist" and I just get confused? Because it's. Its in the DSM-5, both base and edited versions? Idk if its just me being unaware of something, but I genuinely don't understand why so many say it doesn't exist, when it does, and im categorised with that system for NDIS support??