Well, if you are using the camera normally & use flash in a dim / low light situation I don't think you will ever need to use a high shutter speed, you will need to keep the shutter speed at 1/30 to 1/60 hand held. If you have a tripod you can just use slow sync mode. If you do need to use fill flash on a bright day with wide open apertures just get a ND filter.
If you are looking to freeze motion with the flash, all flash can freeze motion by virtue of the short flash duration. The lower the manual power the flash is set, the shorter the flash duration becomes . To do this you will need to shoot in a darkened room, with the aperture already opened, trigger the flash / strobe when the subject crosses the camera.
This is how a picture like a exploding balloon is taken. The freeze motion was not done by the shutter speed but by the ultra short duration of the flash in a darkened room.
The trick is to set up a trigger mechanism (IR light beam or sound) to trigger the flash / strobe just at the right moment to freeze the subject in the frame.
Answered your question?
Under most shooting conditions a hot shoe or remote flash when used with diffusers will add light to the subject & remove shadows. It is the manipulation of the light on the subject that makes a picture bland or stand out.
I too have a friend that doesn't make use of the flash that I bought for him. He finds it difficult to learn to shoot with a flash.
On a personal note, I am multiple flash junkie.