not documented in Matlab?

Both, ishandle(H) and ishghandle(H), are given in doc with only one input argument possibility, however ishghandle(H,'property') produces no error (and can be seen used in that way in guide exported files).

>> x=-2*pi:0.1:2*pi;
>> h=plot(x,sin(x));
>> ishandle(h,'Color')
Error using ishandle
Too many input arguments.
 
>> ishghandle(h,'Color')

ans =

  logical

   0