When you say "accelerates", are you meaning that you have to train that ability and it will raise with higher %?
I founded this guide (in spanish) and i think is only general.
https://i.ibb.co/F6FjzWQ/Entrenos-subidas-totales-y-secundarias-por-semana.png
If are you referring to the elastic portion then yes. If your training outside defense then if you have HA > OD. Then yes it will accelerate OD training compared to if HA was equal to OD.
For example, if I am training Outside Defense then I can see the effect of Handling is (+0.0332).
This means the handling will increase the speed of Outside defense. More specifically, for each level of
handling above outside defense you get a 3.3% increase in training (estimated).