They can check the Countries you are visiting to see if they need a VISA
https://www.mfa.gr/en/visas/visas-for-foreigners-traveling-to-greece/countries-requiring-or-not-requiring-visa.html
https://www.guideconsultants.com/turkish-passport-visa-free-countries-list-2022/
It is up to the pax to do their due diligence
I often check the VISA service site to see what is required then go to the site of the Country we are going to & see if we can apply online or not