Obviously, you cannot cut a Direct Disc at half speed if it's going to played back at full speed. In fact, just the opposite is desirable - the best DD's are cut at 45 rpm. And 78rpm would be even better.
I personally find Direct Disc recording to be way more of a benefit than 1/2 speed mastering anyway. I have A/B'd some of the 1/2 speed and 45rpm reissues of original "normal" 33rpm recordings and found fairly minimal differences in the 1/2 speeds. The 45 rpms make a bit more difference but won't improve an average recording to anything approaching a decent DD.
I personally find Direct Disc recording to be way more of a benefit than 1/2 speed mastering anyway. I have A/B'd some of the 1/2 speed and 45rpm reissues of original "normal" 33rpm recordings and found fairly minimal differences in the 1/2 speeds. The 45 rpms make a bit more difference but won't improve an average recording to anything approaching a decent DD.