Is it safe to use this dimmer on LED bulbs?
Nope

From this LED compatibility guide on Lutron's site, the following output. 



Further, The service manual you link states clear that 


  
  CAUTION: Use “AY-” or “TG-” models only with permanently-installed
  120 V incandescent or halogen fixtures. To avoid overheating and possible damage to other equipment, do not use to control receptacles, fluorescent lighting fixtures, motor-driven appliances, or transformer-supplied appliances.
  


That's it.  It's not "not saying" about LEDs, it's saying very specifically about LEDs, since it allows only incandescent and halogen (which are incandescent).  Open up "See Aridani/Toggler model numbers", and open up "Dimmers" (the only category), i.e. here, it lists several categories and the results in each echo the above. 

Welcome to the world of off-label usage.  Which means UL has not tested this equipment for this usage. It might work, might not, might get magic smoke, it's all on you. 

So the ultimate answer to your question is, shrug...