Depends on the aircraft. If the company operates a widely varied fleet it may just be to streamline the procedure to infact eliminate the possibility of error.
Generally 737 and single aisle aircraft are crosschecked as 1 Crew member can be in control of more than one exit and therefore has double the responsibilty and crosschecking then takes some of that added responsibility away.
Personally I dont think its really required, but follow the procedure as stated in the manual, and I suggest you do the same.