ADDITIONAL SYSTEM INFORMATION :
macOS 10.13.4 and Oracle JDK 1.8.0_171

A DESCRIPTION OF THE PROBLEM :
When a JavaFX application is opened on macOS, there are various way to hide it temporarily:
1/ by clicking on the yellow button on the top-left corner of the main window --> this effectively hides the main window
2/ by going to the top menu [Java > Hide Java] --> this displays a "About Java" popup instead
3/ by right-clicking the icon on the dock, and selecting "hide" --> this displays a "About Java" popup instead

2/ and 3/ should behave like 1/.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1/ Create a JavaFX application
2/ Launch it
3/ Try to hide it by going to the top menu [Java > Hide Java]

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The main window of the JavaFX application gets hidden
ACTUAL -
A popup gets displayed showing the title "About Java"

FREQUENCY : always