He got his data from SPEER. Except it seems he's below starting load from Speer and also from Hogdon.
OP, You might go back to your Speer manual and note they state, "COL tested at." That doesn't mean it will work (as you've found out) or be the desirable length for a particular gun. For any rifle, you should determine at what COL a specific bullet touches the lands and reduce your COL below that by some amount you decide is best. The Speer manual really muddies the water on this. I assume it hasn't changed much. But in the bullet seating section, they do tell you how to make a dummy round to find out how deep a specific bullet needs to be seated to get it off the lands.
It's also a good idea to look at something comparable in the manual. That bullet is used in all sorts of different cartridges so it is easy to look at another 30 caliber cartridge and see how the OAL changes between weights. In my Speer manual, by comparing 308 to 30-06, I see an aberration with the 30-06 COL for both the 168 BT HP and the 150 BT FMJ. Red flag and time to see if there is a typo or if they used some oddball rifle for their testing.