I've heard that kind of justification before.
But having raced Master Worlds 2017/18/19, and having raced Sprint and Scratch in all of them, including making the semis and final on Scratch, and having watched the points racers, for example, I don't think Keirin would bring any different level of risk, considering the racers I've seen on the Sprint Match races.
I'm among those that don't like to crash, but wouldn't be afraid of racing a Keirin against the top 10 of the Sprint Match quali (even on the 60-64 age group we're more than 20 entries).