Yeah, “panes” are now referred to as “tab groups” (on desktop anyway). It’s confusing reading old and new posts or searching for things.
What you see is definitely not normal behavior for Obsidian on a phone sized device.
Can you try making a new test vault and see if you see the same behavior there?
I’m wondering if it’s a plugin (or something) trying to mimic tablet / desktop behavior on the phone.
If it looks alright in a test vault, I’d try the troubleshooting steps with a focus on Restricted mode (no plugins) and restarting between changes you make.
There are also ways to reset the workspace layout to default if the other troubleshooting steps don’t work.