A mixed space-time rotation is simply an hyperbolic rotation in Minkowski space-time with signature [+++-]. This is related to the variation of mass with speed in special relativity.

This is clear from a math point of view. But time cannot rotate as it is strictly 1 dimensional. As said time can only be defined as "difference" between two events. May be you once should read the basics of information theory.

What rests behind is a kind of metric for mass (-increase) that as such can never be homogeneous in 3D because in 3D only 2 rotation are allowed. The more severe problem is that real mass with real dimensions rotating at light speed cannot be covered by such a "relativistic" formalism...

You must strictly separate the time bound dimensions (Usually radial actions) from the fully relativistic static (rotation) dimensions.

So all the above SM equations are fruitless fantasies if you deal with particles!.