It is my understanding that a touring bike is meant to carry heavy loads over "reasonable" roads, whereas a trekking bike is meant to navigate trails with modest loads (similar to bike packing). See here.

Problem is that in English trekking usually means a rugged, extreme form of touring such that we think of crossing Mongolia as trekking whereas using bike paths with the little ones following in a duck row as touring.

Shimano now has a trekking pseudo group, which is basically XT with a triple 48-36-26 crank, basically unavailable in America while not common in Europe.

I do not think that these designations are inspired by shady marketing. They reflect real differences in how people use their bikes.