There are 2 major differences:
1. you have to know the nominal intake closing point. The .020" and .050" are useless, and the K-B correction is a vague guess (based on Vizard's estimate of 30° effective duration diff between lashed and .050").
2. the ratio of variable heats (the exponent in th formula) will vary all over the place between about 1.2 and 1.4 depending on water jacket temperature, compression ratio, EVO point etc. No engine you can buy runs 1.4, the best guesses are 1.25 to 1.3.

BTW: DCR is now a buzzword (yes, that 15 year old at the magazine rack uses it), but it does very little of practical value.