I don't understand the reasons why books do what they do (im sure there is a reason...maybe..lol).
But, in this particular case, The 107 SMK was a COAL of 2.850", 37.5gr of powder with pressure measured in CUP of 50,000
The 108 ELDM was a COAL of 2.700", 41gr of powder with a pressure of 59,300 PSI.
That SMK load real world is a pretty low pressure, legacy gun load. The ELDM load is a somewhat more modern rifle oriented load.
The .243 in general, has alot of under pressured load recipes, like alot of legacy cartridges, due to older guns, lever and pump guns etc. In most "Modern" rifles, with decent brass, your not going to see pressure signs until you get somewhere above 62K PSI, although this also depends on the barrel chamber specs, which can be all over the place on .243's.