So, my understanding from what you wrote is that it may indeed be possible to slowly release the accumulated pressure, but we don't really understand how that occurs naturally yet, let alone how to trigger it artificially.
Given the regularity of previous large quakes, and the fact that the described magnitude 6 quake takes place over a month, it would take longer to relieve the pressure via month-long magnitude 6 quakes than we have until the next large quake. Best case scenario - you could put it off for a few dozen years.
Even if you could relieve some of the pressure, you could theoretically make the big one less intense. It sounds like we're not even remotely close to being able to do it in practice though. (Although if we were, there's no reason why the described magnitude 6 over a month would be a limit.)
Making the big one less intense may or may not be possible. There may be some threshold pressure that needs to be reached. If there is a threshold, then it will either happen or not, depending on the rate at which we relieve pressure with smaller quakes.
I imagine the difference is what we can do vs. what is far beyond today's ability. And triggering a quake is fine even if it releases full force assuming the payoff is we get (for example sake only) a 7.1 quake today and avoid a 9.1 in 100 years.
