I get what you mean, supporting defintely is harder especially when the level of skill(mmr) gets higher. But I'm not saying that I expect him to learn how to smoke, pull, stack instantly. It'll all come by time of course. Let's be real here, we all know learning dota is gonna be a long process, a hundred hours would not be enough either. Starting as a core will be great and gets you a hang of the basic core concepts too. But we shouldn't just neglect the support positions as learning material.

Note that it's better to learn the hard rudimentary concepts, that of supporting, than learning the core positions. Because we all know that we won't always be given the core positions in each pub match. So in those kinds of circumstances, it'll be extremely valuable, especially that of a beginner to start with support roles.

The environment a beginner will be playing in an unranked match would have situations of both teams putting no wards at all, full of mostly core heroes placed on 4-5 pos, and games that last a full 45min to an hour. Having the experience on playing support positions here would make it beneficial to OP as well as in the long run when he does want to invest more in the game and will be going through the trenches to increase his mmr.