Now I'm confused... how are they the same thing?

Thanks gives one point, not one Rep Point -- one Rep Point is given for every 100 singular Thanks given (or the equivalent number received in Rep)... so there's a big difference between one point of "thanks" and the 100 total points required to display as one point in your Rep Power. Your Rep Power is what defines how many points you're able to give when Repping someone... so if I was to give Rep, instead of only giving one point like I would with Thanks, I'd be giving 159 points, that's over 1 and a half points of Rep Power increasing... so it's a pretty big difference.