Above FM does not actually look that straight, an often claimed feature of FM. What's going on?

- FM schedule (often omitted "OT") is straight to a single point (possibly with tiny noise).
- Unfortunately, that does not guarantee straightness between distributions.

DDIM vs Flow Matching.
Note whatever schedule (alpha/sigma, VP, VE, FM) we pick, DDIM always ends up at the same spot:
- DDIM is invariant to alpha/sigma rescalings
- With FM schedule, sampling with either DDIM and Euler (=what FM uses) is the same.