Uh. The relationship between CentOS Stream and RHEL is a bit murkier to me. I'd be lying to you if I said I fully understood how that code flow works.
For openSUSE the flow is "openSUSE Tumbleweed" -> "SUSE Linux Enterprise" -> "openSUSE Leap"
Everytime SUSE creates a new version/service pack of SLE (SLE 15 SP4, to use an example) the sources for that version are provided to openSUSE, and a new version of Leap is released (openSUSE Leap 15.4)
I don't actually work on Leap much, nor am I a SUSE Employee, so there are probably some minutae in that process that I'm missing, but that's the basic workflow.