First off, welcome to fitness.SE!
These two exercises in your example you can indeed learn at the same time. These are mainly moves of pure power.
When people talk about learning one or two skills at the same time, they are mainly talking about more advanced types of calisthenic exercises. Things like handstands, planches, front levers. These don't just require a lot of power, they are also all about technique and proper form.
If you are still learning a handstand and you also start trying for example a planche, it will most likely hurt the progress you'll make on the handstand.
If you want to learn more advanced calisthenics, aim to learn about 2 to 3 moves a year and really master them before moving on to the next.
If you have any other questions, let me know in the comments.
I hope this helps!