For instance, when you select "I speak Spanish", you have no "immersion" tab.
It's because they're not out of BETA yet. Those that do have immersion are usually the original courses that were on Duo, whilst the ones that don't are contributed courses. This is because they're not "stable" enough to be out of BETA.
Annoying, isn't it, I've tried to upload something in Russian to no avail. :-(