Ahh, well I wondered that myself! Actually, I had an old antiX-14 (pre-antiX-15 release) on this old P-III machine and it was working fine until I accidentally borked it (story in another thread). So, I decided to start over and I was going to redo it with the proper antiX-15 but anticapitalista suggested that if I wanted to stay with Jessie I should just use 16.3. I did that, as I wanted to start this machine off with a working Jessie based system.
I would have skipped up to antiX-17 except I don't have a DVD on this old machine nor a working USB for booting antiX-17. So, antiX-16 it is. It is working and it is a step up from the original antiX-14. Not sure if I will attempt 17 on this later or not. I have other P-III and P-4 computers that antiX-17 are on.
So, if I am understanding I could have chose "testing" at install and would have essentially ended up with a rolling release of Buster. I may try that later. But I'm still learning about how to setup Debian stable and don't need the headaches yet.
Seaken64