Sourdough more rise in the oven
Yippy for you. The term for the expansion of the loaf in the oven is " oven spring " and it is a good thing. Artisan bread bakers cut the top or sides of the loaf so it does not tear when it springs. There is tool called a lame' for this purpose. It is a razor blade mounted on a stick or wand so that it is curved. To use you need to perfect the technique of scoring the loaf with a flick of the wrist. Sounds like you have nice healthy sourdough.