The fact that the BU credits eclipse the rest of the projects has no bearing on the rewards!!! Gridcoin accounts for the difference, BU miners get the same share of the daily mint as the rest of the 34 whitelisted Boinc projects by Gridcoin.
Thanks for the explanation. Is there a decent info-graphic that shows how this works? I think it would really help bring the complexity down to earth for the "casual cruncher".