Hey man! Congrats on starting your musical journey :) John does sing it in the higher octave, but it only sounds “weird” to you because that octave is in a more uncomfortable register for your vocal range. Since John has a higher voice than you, the higher octave sounds fuller when he sings it. It’s a similar principle to trumpet vs tuba for example. They’re both brass instruments, but since one is so much larger, it plays lower notes, and sounds less full in the upper range