Is bending on piccolo strings a thing?
Yes, as long as the tension is low enough to be comfortably bendable and they do not reach their break tension.
But unfortunately most piccolo sets, such as the D'Addario one you use, are designed to have tensions equal or similar to a typical E1 standard set so have high tensions that make bending difficult. Look for lower gauges for lower tensions.
The Ken Smith 'Custom Piccolo' set has lower gauges for lower tensions, i suggest trying that one.
The standard Ken Smith piccolo set contains .030 .040 .050 so has similar tensions to the D'Addario set, so is no better.
If the GHS set contains .030 .040 .050 then that will also have similar tensions to the D'Addario set, so is no better.
I've been playing a piccolo bass for a little while and i've found doing bends is much harder than even on bass strings
See your other thread i replied to. Even if at the same tension, thinner strings 'feel tighter', especially in terms of playability. Perhaps one reason is that thinner strings cut into your fingers more when bending.
If you're using D'Addario, they're usually Hex-core strings and a bit stiffer. Try a set from another brand that's round-core like DR, and you should find those bends to be much easier.
Structural stiffness does not affect ease of bending. Ease of bending is determined by the tension (according to mechanics).
my D string keeps breaking with just half step bends
See your other thread i replied to for why.