A very rare event, like the Yellowstone blasts that (appear to) happen every 600,000 or so years. We’ve never seen them, but the evidence points to them.
No evidence points to them, there just happens to be a volcano cookin’ somewhere all the time. The same thinking led to impact craters on Earth being labeled “cryptovolcanic”, and the lunar surface — which is covered with impact craters — being attributed to volcanism.