I looked at my JCA and it has "no support requirements" listed.
My guess - have you done a disability support program? Have you been in the DES stream at a Job Provider or been in a training program assigned to support you as a disabled person?
If you have at least 20 points on the same table you're not supposed to have to do POS. If you have at least 20 points between multiple tables then the POS requirement kicks in. It may be that they want you to do a POS even though you have 20 points on one table (mental health)? I'd check in at the local office if they're at all helpful and ask.
This is what I'm thinking it may be (scroll down to POS):