I have to completely disagree with you here. I'm not sure about the rest of the world, but in New Zealand there is a big distinction between a TH and LH lock. In New Zealand the TH locks always wear 4 and pack on the right hand side of the scrum. LH locks always where 5 and pack on the left hand side of the scrum. You can watch any ITM Cup/Super Rugby game from New Zealand and you will see exactly this.
I'm not sure where you get the idea that Thorn packs on the LH side - he has always packed on the TH (right) side for the Crusaders/AB's (e.g. directly behind Owen Franks). Likewise I have only ever seen Bakkies Botha pack on the TH side. If you look at any youtube video of him in the scrum of either Thorn or Botha they are always on the right hand side (see
http://www.youtube.com/watch?v=WqcYaWOhvy8 - a series of scrums 5 mins in clearly shows what side Thorn and Botha are packing on). Ali Williams generally packs on the LH side, though does pack on the TH side occasionally (such as when paired with Sam Whitelock). Nathan Sharpe is a LH lock (wears 5), hence always packs on the left side, as did Matfield (at least in all the matches I saw him play....).