I’m curious why you’re interested in what’s changed in Leap if you’re currently a Tumbleweed user. Because Tumbleweed is an upstream of Leap. Also, Tumbleweed made this change 8 months ago, making SELinux the default MAC. If you installed your OS before that date, that change doesn’t affect you. Although AppArmor is still available as an option in Tumbleweed.
I also know that the openSUSE project is in the rebranding phase, and it’s important to remember that distributions like Tumbleweed and Leap are community supported, and some developers contribute to the distributions on a volunteer basis, even if they are SUSE employees.