Answers
At this moment, such an issue as the one you refer to has not been officially raised by any competent institution or authority. Thus, this must be only rumors, without any substance whatsoever. With regard to the most updated residency requirements you refer, please note that they have pretty much
remained the same since the program came into force, and according to the pertinent provisions a third-country national can legally acquire the Greek resident permit through real estate ownership in Greece, provided that the value of such property is at least 250,000.
I am not aware of any EU Parliament directives which would restrict you from investing in Greece and obtaining a Golden Visa for you and your family without having to permanently reside in the country. We have not seen any such restrictions in place. As far as I am aware, Greece remains the best option for property investment and an EU residency visa in Europe at the moment.
There is no problem according to the Greek law, which is effective.
The government of Greece introduced by Greek immigration Law 4251/2014 is a procedure to obtain resident permits, which can be renewed every five years for owners of real estate by third-country citizens, the value of which exceeds 250,000 euros. It adopts a friendlier stance toward those who wish to own real estate property in Greece. Every EU member-state could set its own internal laws with specific conditions and terms, but they have to be in compliance with the European framework and regime. There is no space for rumors like these. The Greek program is a very flexible and advantageous program, and there is no point in claims like this. Furthermore, most existing European residency programs by investment do not require a minimum stay of the investors in the country.
With the purchase of a property of 250,000 euros, the buyer, his wife, their minor children and their parents acquire a resident permit.
Please be aware that Greece's investment program for obtaining a Golden Visa is really easy and flexible. It covers underage (under 18 years old) members of the family as well for a not really high amount of investment of 250,000 euros, either for obtaining property or corporate investment(s). So I suggest looking into this more carefully, as it doesn’t violate EU law as you mentioned.
The deal is not unstable or unsafe. Do not believe in rumors. In Greece as an immigrant you have to invest a certain amount of money in funds or real estate. Living in Greece is not an essential requirement, as the resident permit is based on the investment. Ask for advice from a Greek advocate.