My recolleciton is the same as yours -- that Hood wisely ordered the men not to fire during the charge, knowing that it would break the momentum of the charge. Off the top of my head, I believe that he ordered the troops to fire as they reached Boatswain's Creek, and that concentrated volley unhinged the first Federal line on the other side of the creek, leading to the collape of Federal resistance in the successive lines up the slope. By the time the troops reached the crest where the Federal artillerywas located, firing was probably on an individual basis, or at most by volleys from company sized units.
Certainly, however, the charge of the 4th Texas and the 18th Georgia, supported by Law's Brigade to their left, ranks as one of the finest in the entire war, and established the reputation of John Bell Hood as one of Lee's finest combat commanders. He had an enerring ability to size up a tactical situation and to exploit it to the fullest, which he demonstrated again and again on the field.
The only significant ommission in "Chickahominie's" report was his ommission of the Hampton Legion as a part of Hood's Brigade -- but it had only just joined at Ashland on the 25th, and was on the far left of the brigade, which with the 1 and 5 Texas regiments participated in the charge, but in the woods, and more protected from Federal fire. Its loss was slightly over 12% of those engaged.