I am a Greek-American guy with strong connections to Greece and my Greek-heritage. While the "tradition" to which you refer had its place among the noble classes of Greece in antiquity (and notably Athens circa 500 B.C.), and to an extent during the Alexandrian period, I can assure you that nothing so formalized exists in the Greece of today- or the past 2,000 years. One-thousand years of conservative Orthodox Christianity during the Byzantine Empire (353-1453) largely did away with that, and of course during the following 400 years, during the Ottoman Empire (1453-1821), Greeks as a nation, Greek as a language in general were even further repressed- let alone the lofty idealistic masculine ties to which you refer: Greeks were lucky to stay alive, and live as serfs. With the re-birth of Greece as a nation in the late 1820s, Greece adopted most of the norms of the rest of Europe- while still holding on to some of the Turko-Asiatic traditions of the Ottoman period. The "development" of boys via older males via erotic channels was not something terribly acceptable in either sphere of influence.
Modern Greek history (up until the mid-1970s) has been quite turbulent, marked by many wars, periods of great poverty, emigration, betrayal by its allies, threats from its neighbors, etc. It has been a hard road, and as a result, for much of its modern history, Greeks had become somewhat "hardened." That being said, a certain machismo developed within the society, where the (strong) male was celebrated in general, but this was usually in an ultra-heterosexual context, with perhaps some strong homoerotic undertones. While friendships among men were/are perhaps more intimate and affectionate than in many other western European and North American societies, active engagement in homosexual relationships was greatly discouraged. Let's not forget also that it became- once again after its liberation in the 1820s- an orthodox Christian state.
Of course, even in the heyday of the macho Greek male- in the fifties, sixties, and seventies- the most macho Greek male, when asked, might refer back to the homoerotic relationships of antiquity with a vague admiration, with a certain sense of societal nostalgia; with a twinkle in the eye almost. Not in a perverted way; more as if to say "not right for me.....but, our ancient ancestors may have been on to something." Greeks in general are proud of their history, and put much faith in the (greater) knowledge that they perceive their ancient predecessors to have posessed. Of course, many of these "macho Greek males" could and would engage in clandestine one-off homosexual encounters, but they would never in a million years identify with being "gay," nor would they see themselves as being "mentors" to their male sex-partners in any way.
Greece since the seventies has progressed economically, politically and socially by leaps and bounds. The standard of living and way of life is indistinguishable in most aspects from that in the rest of Europe and the U.S. In many ways, it is now more progressive than the US -especially with regard to women's rights, and the assertion of women as a group in general: everyone now talks about how Greek women have "come alive" in the last few decades. Modern "gay" culture has also become accepted for the most part, especially in the larger cities and in places like Mykonos. But still, that is something quite different and apart from the "Greek Tradition" to which you refer. On the other hand, there has been relative peace and prosperity, and so society has "softened" in many ways. The hard, macho Greek male is slowly becoming a thing of the past as well.