In terms of SPICE, NJL5501R is just a combination of two LEDs and a phototransistor, nothing special. What do you expect from a NJL5501R SPICE model? How should it represent the non-electrical signal generating the output.
These aspects can be modelled in a SPICE simulation, but they are beyond the responsibility of the sensor manufacturer. It's system rather than device simulation.
You can .include a lib file in your LTSpice design and connect it to a symbol. Check if the pin order expected by the symbol is identical to that of the subcircuit in the lib-file.