The song... I believe... will have "worry" and "every" on the 1.
Now if you were strumming easy guitar you would be strumming there and changing there. But reggae guitar really is going to hit the 2 and 4
So the beat stacks up like ... among other things....
Wor.... 1-rry
------------Guit --- 2
-------------------Bass drum -- 3
-----------------------------------Guit --- 4
Sooo.... if you can sing it, you really want to do that, and then just play your guitar on the 2 and 4. Which will mean..... your hands may be moving and you may be singing Worr but you might not hi the actual chord until the second half of word..... Now if other instruments were playing they would actually be sounding.... so your voice is actually changing chords before you strum.
It really depends on how you are going to play it.... I think the book is correct but the video, for what's trying to get across is probably ok too.
Or as Bob said... "He who feels it knows it".... If you are not feeling it keep moving things apart in time.
To me.... this song is really about singing and the guitar is simply along for the ride... As is the heart and soul of Reggae... it's really a singers music so even for solo guitar you still need to really be able to sing the rhythm even if your pitch is not great.
Watch this guy... I don't know how he is counting it, but in reggae when the T hits the three YELOW strings that is 3. Then he hits m+i on 2 and 4 and on a center red string he hits a red T == that is 1
So is you watch all that you see his changes match the book and he's playing the bass on 1. Every time he clacks his nails that's 3.
This would actually be a pretty good way to play it but still a little busy with that regular bass beat though... it's really hard to do all that stuff at once because you are emulating at least 4 instruments plus singing.
https://www.youtube.com/watch?v=rOSKYSpMsQk