Except the IRB rankings are demonstrably nonsense! The idea that England are currently a better team than Wales is, quite frankly, pretty ridiculous.
Even worse, if Wales lose on Friday, they will drop to 8th place! You could argue that the only teams in the world who are currently better than Wales are New Zealand and South Africa. We'll see if Australia are on Friday. France are not playing good rugby, and neither are England. Ireland are the closest of the home nations to Wales.
If Wales win, they can go into 2nd place, especially if France lose (as expected). But you could still argue that South Africa are better than Wales, yet they would be below us.
I pay no attention to the rankings anymore. You don't really learn anything of any use from them. And yet these things are used to determine the seedings for the next World Cup!