Why particles are not aligned to view when used in component (unity 2d)?

[Piotrone]

I’ve managed to have billboard particles aligned to view/camera when the particles system is a game object. But when the particle system is used as component of a sprite, billboard particles are not aligned to view (particles are visible if I switch off from 2D mode, see second picture attached)

[Piotrone]

Changing “Render Mode” (under Renderer) to “Mesh > Cube” fixed the issue: I see the particles in 2D mode. Not sure why.