I find arguments like this easy to agree with but difficult to apply in practice. I've heard many an argument about what really is or is not realistic. And sometimes what is or is not validly fantastical is easy to agree upon, because everyone gives "proper fantasy" a margin of error that they don't give to the mundane.
It may not help, but here's an example: my current campaign is set in a "D&D-ized" post roman Britain (or "grimy Arthurian"). All the players are aware of this and on board. This is our "real like" baseline. I have a half dozen books or so on the subject (plus the internet) and we all make an effort to imagine and assess the world from that vantage point. Moreover, I've made it clear that the world works, physically, like the "real world" except when magic (or game mechanics!) says it doesn't. So, when the party is trudging along a cart path in the rain, they get wet and muddy and can't see or hear as well and therefore they (the characters) end up grumpy and watchful. When they get to town and have to deal with the local authority (be it a governor in a still "romanized" town or a chieftain in a defiantly celtic village) we refer to those archetypes (okay, stereotypes -- I am at best an armchair historian and probably more like an ottoman historian) to determine how people act and react. But there are elements that are decidedly not "real like". The Saxons and Angles haven't showed up at all yet (though they are coming) and the Picts are Half-Orcs that worship Cthulhoid entities locked beneath the world by the Irish Elves 2000 years ago. The players know this stuff (some of it because it is common knowledge, some of it because they have discovered it in play) and respond accordingly. In other words, where it is not "real like" and is something that is character-knowledge, it adds to or supplants the "real like" baseline.
Note that I think "real like" can be "unreal". If one is running a purely Arthurian game, for example, "real like" may include real world physics but the idealized "reality" of Arthurain Romance as it applies to culture and society. The same for your "bog standard" D&D campaign. Social, cultural and historical "real like" often gets short shrift, but physical and psychological "real like" can still be used as a baseline. Problems arise, I think, with settings like Dark Sun or Planescape (which are cool, no doubt) because they deviate so much from both the D&D-isms and "real like" worlds that unless your players (and the DM) are very familiar you end up with a lot of game time spent on exposition, plus the very real possibility of retro-action ("My character would know that so wouldn't do that.")
There, I think, lies the real value of "real like" -- it speeds up and supports "natural play".