In addition to changing the defaults to new accounts, I have also retroactively changed the project preferences for all users who have never set their own preferences. Note that this change ONLY applies to people who have never set any preferences. If you've ever set any PrimeGrid preferences, nothing was changed.
Chances are, if you've never set any preferences, you either don't know that there are preferences to be set, don't know how to change them, or don't care what tasks you get.
I therefore suspect that most people whom this will affect won't notice any difference, mostly because they're not paying attention to what their computer is doing at PrimeGrid. Perhaps they might notice that it's no longer running absurdly long tasks, which they'll likely appreciate.
If you are affected by this, and prefer the old "send me anything at random" behavior, just go to the project preferences page and select all the CPU sub-projects.
My lucky number is 75898524288+1