Title Says it all; If you conjure a block and set it to 1 tick, there is no hitbox or particles, if you are casting every tick on leggings, the conjured block acts like a ghost block; you can hit it with a raycast, but you cant walk through it.

The hitbox part is fixed, but the particle part is intended.
Conjured blocks tick randomly so there's a chance it doesn't show up, although now that chance is rather low.