Phototransistor resistor value help
The App bulletin is likely using a OPB860/870/865/875 part which has a lower Ic(on) rating (0.5ma). Your OPB36xT55 part has a higher min Ic(on) so it makes sense that the R2 value can be lower.  (Also note that the exact p/n OPB365T55 is not actually included in the data sheet.)

Your calculations for R2 and R1 are correct assuming a Vce(sat) of 0.4v, and an LED current of 20ma.