As of TU16.1, focus is enabled correctly with GR9 scopes, but not with Merciless scopes.
Even though the Mercyless scope has a higher magnification than the GR9 scope.
Focus is enabled when aiming with scopes 8x or higher.
The magnification of the Merciless scope is not specified, but comparing the screen when aiming with the scope, it is clear that the Merciless has a higher magnification than the GR9.
Therefore, not being able to activate focus with a Mercyless scope is problematic.
This problem is not limited to Focus only, but Perfect Focus also has the same problem.
The video in question can be viewed at this URL.