Since CAD software is typically using single threads for most commands, they will benefit from the boost speed of at least one or two cores in the CPU. Only a few cores will run at very high boost speeds simultaneously, and the reason for this is that the CPU would be overheated if all cores would run a boost speeds. So, it will not overheat if they limit boost speeds to only one or two (or at least very few cores). Now that is typically not a problem when using CAD software since most commands would use single threads anyway (which benefits from boost speeds).
For multi-threaded tasks you will of course benefit from the the number of cores although not at all of them can run at boost speeds, because the number of cores is what gives you the speed in such cases.