Teck will do very well by the appreciation of those shares purchased on the open market right now.

They cancel the shares that they buy back, there will be no appreciation. In theory they are making the remaining shares more valuable because there are fewer of them. In practice this doesn't seem to have worked very well. However, if they intend to buy some other company by offering shares, then they can announce that they have already bought those shares so Teck itself won't be diluting from a number of years ago--if that makes sense.