What do the dimensions describing the crimping tools mean?
When expressed in mm², it gives the wire section. Basically, this corresponds to the AWG of the wire. There is a table with corresponding values here.

If it was given in mm, it would represent the crimping die width (see image):


At no point the pitch (2.54mm) is relevant when crimping wires. You select the crimping tool depending on the wire size, not the connector pitch.