Kalash are a relic of Proto-Indo Europeans is a catch all with no evidence. Such claims with no actual evidence is not worth talking about. But I guess the Greeks did leave behind influence given the new and improved muscled Buddhas that resembled Apollo
The Kalash language is a mix of the languages found in the region- Tajik, uzbek, tartar, persian, etc. But, there are Greek words for woman, washing, winter, greetings etc used among the several Kalash tribes that are Greek. While even that can be explained under the PIE theory, your statement of 'absolutely nothing to do with Greek' does not stand.
But further study- genetic and archeological- is necessary.