Steps to reproduce:

1. Download and import attached project. "ParticleSystemEmit.zip"
2. Open scene: main
3. Press play.
4. Press A to emit particles.
5. Change boolean value in script attached to particle system to see difference between using EmitParams and not.

Actual result. When overriding particle position it ignores the shape.
There should be a boolean value that:
T. Overriding the position of particle also overrides the shape.
F. Overrides the position of particle but also keeps the shape.

Reproducible on all versions of Unity.

Similar results can be workarounded moving whole emitter.