Coronado drains get more use than most people realize. Between the older homes and the busy kitchens, a Coronado drain has usually been collecting grease, soap, and buildup for a long time. So when it clogs and the snake clears it, this is what really happened. A hole got punched through the blockage. The coating on the pipe walls, all those years of it, stayed put, and it starts closing the hole again the day the plumber leaves.
Hydro jetting takes the opposite approach. Instead of tunneling through the buildup, a high pressure stream of water washes the pipe walls down and carries the buildup out of the line.
Is it always necessary? No. Hydro jetting is worth it on the jobs that need it, and you'll be told when yours doesn't. Some clogs need nothing more than a snake. The contractor looks at what your line is actually doing, explains it plainly, and recommends what fits. You decide from there.