The only issue is that with a 2 speed motor, going FROM high TO low should be done with a slight pause where nothing is connected, because you need to allow the motor magnetic fields to collapse before re-energizing it. Going from low to high isn't the same, the motor just kicks in and there may be a little current spike as it catches up. But going from High to Low, if the magnetic fields from the High configuration are still there when you energize Low, the motor is still a generator and you are now connecting two power sources that are out of synch with each other. Bad stuff can happen; blown fuses or tripped breakers if you are LUCKY, broken motor shafts or other parts, fried windings and/or nasty voltage spikes that kill nearby electronics if not. The magnetic field collapses really fast on a small motor, less than a second, so it doesn't need a long delay.
If you have a mag starter setup to change speeds, that delay is usually built-in to the controls because of the mechanical timing of the devices in that there is usually a mechanical interlock that ensures the High contactor is open before the Low contactor can close. If you have a manual switch, you usually have to pass through an Off position to go from High to Low, that gives you the delay too. Just don't roll your own switch configuration that eliminates that pause.
