I had this same idea with Vauban since it seemed like a natural and effective interaction, and was also disappointed when I realized it doesn't work. I'd love some explanation for this. My guess is that it doesn't apply to ragdolled enemies. I checked and it does work as expected with Ensnare, producing a similar effect, but I'm pretty sure it would be stronger using Nidus or Vauban meatballs.
This is a nice idea, but further proof that DE doesn't remember their own game mechanics. As someone above mentioned, this doesn't factor in augments that add hold functionality (i.e. [Smite Infusion]), and what's more, it completely ignores the fact that some tap/hold abilities (most obviously Thermal Sunder) can be INJECTED, meaning this option must exist for everyone. No idea why they didn't just add the option for every frame.