Every town on this coast sells the two together, and I could sell you the same thing. It happens to be defensible, but only if you pick the right class, so here is how I would pick.
What surfing does to you
Hours of paddling, which is repeated shoulder work in a narrow range with the spine extended and the neck held up. Then short, explosive pop-ups. Then more paddling.
The output is predictable: tight anterior shoulders, a stiff upper back stuck in extension, hip flexors that have been shortened on a board, and a neck that has been craning for four hours.
Which is why a hard flow class is a strange choice
A vigorous vinyasa is largely chaturanga, plank and downward dog, which is more shoulder work in a similar range, on top of the shoulder work you have just done for a morning.
People do this constantly, then wonder why their shoulders are wrecked by day five of the trip. It is not a mystery. They trained the same pattern twice and called the second one recovery.
What actually answers it
Thoracic rotation and extension work, hip flexor length, and anything that opens the front of the shoulder without loading it. Restorative work after a big session. Alignment-focused classes, because they will spend real time on the upper back that everything else skips.
If you have surfed hard in the morning, the useful class in the afternoon is almost never the hardest one available.
The order matters
Yoga before surfing: light, mobility, nothing that fatigues the shoulders.
Yoga after surfing: slower, longer holds, and prepared to be unglamorous.
The honest version
I am not going to tell you yoga will make you surf better. What it does is keep you surfing for more days of the trip and more years of your life, which is a better offer anyway.