This is intended as a fix/workaround for a different issue. Currently, disabling the HUD disables all of the GUI rendering. However, there are some parts of the GUI rendering that should never be disabled, as doing so could provide a competitive advantage to players during PvP combat.
The workaround is applied to screen effects caused by flashbangs, plain flinch, binoculars, and scopes. Sorting this out is on the to-do list for the next time the lower-level UI features are being worked on.