I think you are proving my point, not yours. In 1864 Grant could afford to continuously destroy and reconstitute his own Army so he did. No genius military tactics there, just shear butchery and attrition. Nothing to really study or learn from on the Union side in that campaign.
Lee resorted to exactly the same tactics at Malvern Hill and at Gettysburg. No genius military tactics there. Nothing to learn or study from the Confederate side in the Gettysburg campaign. One difference, by the end of the Overland Campaign Grant won his objective, the ANV was locked up like a tiger in a cage at Petersburg. Lee’s Gettysburg campaign ended with the ANV retreating out of Pennsylvania having lost 1/3 of it’s soldiers as KIA, MIA, captured or wounded. Another difference, AOP casualties, in the Overland Campaign, contributed to victory. Casualties in the ANV, during the Gettysburg Campaign, contributed to defeat. In war, victory is the only thing that counts, there is no second place award.
I think Grant was smart enough to know that northern Virginia as a theater was a lot more constricted than was northern Mississippi. If he made a mistake against John Pemberton, no big deal. If he made a mistake against Robert E. Lee, you get Cold Harbor. I think Grant had the measure of his opponent in both cases.