Using 0.85 Mjup, 1.7Rjup, the mean density is very low, 2.1461E-01 g cm^-3. If the hot jupiter spins at 3.7 day rotation, the rotation is 2.39 km/s at the equator. The Sun rotates near 2 km/s. If WASP-79b spins faster than 2.39 km/s, it is likely not tidally locked.
One more point I note here. The May issue of Sky & Telescope has an interesting report on exoplanets, and WASP-79b fits the profile very well. "...But we now know that a model based only on our solar system is misleading. From systems where planets orbit two stars instead of just one (Kepler-16b) to those with Jupiter-mass planets on orbits of just a few days (Kepler-435b), our observations since the first exoplanet discoveries in the mid-1990s have continuously surprised us with a puzzling diversity of system architectures. Our solar system is not the blueprint we once assumed it was." ref - Revising the Story of Planet Formation, Sky & Telescope 139(5):34-40, 2020
"These observations showed no signs of "Rayleigh scattering," a phenomenon in which small, high-altitude dust particles cause wavelengths of starlight to disperse differentially."
Ouch. No, Rayleigh scattering in the Earth's atmosphere is not due to dust. It is scattering by the molecules of nitrogen and oxygen in the atmosphere.