Using DWM window manager, the gnupg pinentry dialog is no longer floating. Instead it gets tiled like a normal window. DWM floats all dialog windows by default, so I'm guessing something changed in pinentry so the window is no longer identified as a "dialog".
I can isolate this change between 2.1.21 and 2.1.23.
uname -a: Linux desktop-arch 4.12.8-1-ARCH #1 SMP PREEMPT Thu Aug 17 08:37:20 CEST 2017 x86_64 GNU/Linux