I couldn't say whether you're in the minority, but I would say that the reasoning you give for your position strikes me as specious. This is a complex issue with many facets that need to be unpacked. For example, your implication that a person walking off into the woods leads to no additional demands on others only follows if you also feel that a person's decision also waives family's and friends' right to request a search and rescue operation. Because, as that article points out, it's typically not just their business. Search and rescue is dangerous and may put additional people's lives at risk. And I would, in turn, say that that position is only tenable in cases where someone has done something like filed a signed affidavit saying, "Yes, this is my attention," with the local authorities. Otherwise there's not necessarily any tenable way for authorities to tell to worried loved ones, "No, this is what they wanted, so we can't get involved."
And it's clear from McCandless's own actions - especially leaving a note on the bus asking for help - that he did not really understand what he was getting into, and did ultimately desire help from others. So, ultimately, even he himself did not believe that his fate was nobody else's business.
Finally, despite your assertion that, "It's not a question of moral or ethics," your entire position is inescapably an ethical position. Because one's opinion on whether society has a responsibility to attempt to protect these people, or whether it's better to simply leave them to their fate, is, by definition, an ethical position.