That's 40% of "ton-miles" - trains disproportionately move heavy, cheap goods (i.e. aggregate, coal), which makes that number potentially misleading. The percentage of freight moved by rail by "value" is closer to 15% (trucking is ~65%).
Why would one want to emphasize value over weight? If I load up a train with extremely expensive metals, jewels, artwork, etc. couldn’t I raise a countries rail by value measurement overnight?
I agree it's good to consider the whole picture, but ton-miles are probably the most important to consider given the increased diesel required to truck heavy loads, correct?