User blog comment:B214/Volume 21 info & spoilers/@comment-71.205.30.36-20160407022108/@comment-71.205.30.36-20160407172108

DxD is probably "weakened" by having a block or series of blocks put on its power output. Just like when Issei first became a devil and Rias had put blocks on him so he could get used to the power. She took off the first one just before the match with Riser and the rest were blown away when Issei entered Jugernaut Drive.

It also makes sense IMHO that the attribute of "Infinity" could not actually be nerfed, so limiting Issei's ability to tap into it would make more sense.