FsStayOnTop different behaviour with ARM-Linux compared to Intel-Linux

[att2]

Hello,
My boss is reporting that the FsStayOnTop functionality is different on ARM-Linux machines (Odroid C4) than on Intel Linux (Virtualbox VM with Linux Mate 19). Both linux distros have GTK2, both distros have kernel 4.9.x .
So a different code has to be written depending on for which Linux-system you are cross-compiling the same code.
Can anyone confirm this ?

[PascalDragon]

Can anyone confirm this ?

Do your compared systems have the same window manager? If not, then welcome to the wonderful world of differently behaving window managers...