IL, SSDI, permanently disabled. Confusion about SLMB vs. SLMB+ eligibility. Could I could be dual-eligible for full Medicaid/medicare?

What does it mean to be, "eligible for a separate categorical Medicaid eligibility group?" I keep seeing this to differentiate between the SLMB and SLMB+ but I don't know what it means.

I currently have nothing. My re-determination was submitted late and I've waited about 2 months so far.

Before that I believe I had QMB with a spenddown of like $80 which is confusing to me. I understand mathematically (I think) but why didn't they just put me in SLMB?

1. Could someone explain to me why it is better to have QMB with a spenddown than SLMB with no spenddown? Because a spenddown disqualifies me from dual eligibility, if I have that right.

2. Why don't I have the +? What would the qualifier need to be in addition to 107% FPL and SSDI?

Thanks to anyone who helps me work through this!

I've been googling for weeks. I should have just asked sooner.