Transit Duration Parameterization?

[eas342]

I noticed that the orbits.transit parameterizes the lightcurve in terms of duration.
https://jax.exoplanet.codes/en/latest/autoapi/jaxoplanet/orbits/transit/
Traditionally, I have seen transiting planets parameterized in terms of semi-major axis divided by the stellar radius, a/R*. Is there a reason duration might be better to sample? I'm wondering how one might deal with a non-circular orbit though, which has a non-trivial transit duration.