BUG or Design Flaw: when an external monitor is connected & one of the monitors is put into full-screen mode, the other monitor is blacked out, rendering it completely useless to the user.

Use case:

I am learning a new skill in Logic Pro.

I find a tutorial video online that I want to watch on one screen, while I follow along in the actual Logic Pro app which is active on my other screen.

Steps to Reproduce:

1. Open the tutorial video and drag it to the external monitor
2. Open Logic Pro on the main monitor/screen
3. Navigate to the external monitor and click the "full screen" button (usually in the bottom right corner of most video players or sometimes the keyboard shortcut "Command-F" works)
4. Notice that when you click the "full-screen" button, blackness slides over the main screen, rendering it useless.

There are MANY use cases that would involve this workflow. In fact, one could argue that the MAIN REASON to have an external monitor is to view 'reference' information/graphics/instructions in one screen while performing some primary action on the other screen. This bug and workflow also pertains to the SideCar feature (using an iPad as an extra monitor).

Can someone at Apple PLEASE look at this bug or design flaw and realize what a detriment it is to a very common and desired work-flow.

If there is a workaround PLEASE let me know in the comments. Believe me: I have tried tweaking the settings in the Mission Control (within the System Preferences - or Settings, depending on which version of OSX you are using).

This issue began with whatever OS version introduced the "Spaces" feature, and I have tested on several versions of OSX and it occurs on all of them.

BTW: I have spoken with MANY mac users and have not found ONE who isn't annoyed by this "bug" nor who uses or enjoys the spaces feature.