A different kind of Safe-mode?
After doing some more research specially on Xposed itself, found out this way of booting is a fail-safe option to disable Xposed Framework at boot time which seems to be a feature of the framework itself and have nothing to do with Android core. As mentioned in this thread:


  Xposed for the most part is STABLE and SAFE. However, installing an
  experimental module or an old module can cause a boot-loop. If this
  occurs, there is a fail-safe switch to disable Xposed and exit the
  boot-loop. To disable Xposed, tap one of the hardware buttons (the
  Power button or a Volume button) on your device, SEVERAL TIMES, during
  startup. This means that pressing the Volume Up button, for example,
  multiple times (during startup) will eventually disable Xposed and
  cause your device to boot.


It says to press ANY of hardware buttons several times, so i was pressing power button several times! That's it!

Note that you might need to reinstall the framework after disabling it using this method. Rebooting might not reload the framework again.