I don't think that the beacon works that way. The way I interpreted the comic the beacon has been active for the two years and still no help arrived.
Destroying it doesn't really change anything, most likely it wasn't working anyhow because otherwise you aren't stranded for two years. It might just make it easier to accept rescue isn't coming. And doing it voluntary because you prefer the lifestyle could be good moral boost.
But yes, if you are voluntary on an island you want means to contact help. What Masafumi Nagasaki did sounds pretty sweet sometimes. Living naked and alone on an island just getting groceries every few weeks for 30 years.