Yes, this works and is the best way to do what you are asking.

Using a Y cable on the Aux Switch you could even set one of the three switches to tap tempo on TimeFactor, the next switch to tap tempo on ModFactor, and the third switch to tap tempo on both. Here's how you would do that:

TimeFactor AUX settings:

TAP > TIP
FS3 > T+R

ModFactor AUX settings:

TAP > RNG
FS3 > T+R

Just keep both stompboxes in Bank Mode for this to work correctly. 

Alan