AQ question about x265 3.0_RC version

[Former user]

I find that aq-mode default value was changed from X265_AQ_VARIANCE to X265_AQ_AUTO_VARIANCE in 3.0_RC version. And I have test 3.0_RC version vs 2.9 version at no tune operation, the former can get 7.4% bdrate reduce than the latter one. So my question is that why don't change the aq-strength from 0 to 1(default value) at the tune psnr operation.