Mac OS Command+Tab does not switch back to Full Screen Window

[simonglet]

(Firefox Version: 115.7.0esr (64-bit), Mac OS 10.13.6 High Sierra)

1 - Launch a windowed application on the Mac (App1)

2 - Launch Firefox with 2 windows

3 - Set one Firefox window in Full Screen

4 - Switch to the Firefox Full Screen window

5 - Command + Tab to App1

6 - Command + Tab to get back to the Firefox Full Screen Window

Expected Result: The Firefox Full-Screen Window

Actual Result: The Firefox regular Window