I wouldnt say they think that.
@gyngyn can correct me if I"m wrong but the reason they treat 3.8+ all the same is because after a 3.7 the difference between the 3.7+ and 4.0 is the difference between
having a 90 percent and a 93 percent in all of your classes on average. Difference between 3.5 and 3.7 is the 3.5 could have had several B's and some C's as well. The 3.7 probably has mostly A's and A-'s with very few
B's and probably no C's. Thus the transcript of a 3.8 and 4.0 is still splattered with with all A's regardless of whether or not they are A-'s or straight A's.
Plus the lower you get on the gpa scale just like the MCAT scale each gradation gets larger and larger.
Difference between 39 MCAT and and 36 MCAT? Not very large. Difference between a 32 and a 29? 15 percentile difference.