I'm sure that the website owner provides that rating / percentages table as a resource for dobbers. So we can't really put dobbing aside in this discussion.
In fractional odds terms you're right, but I'm sure that most people when they see on that website that a horse traded inplay at 50% BSP, they think that if BSP was 5.00, the horse traded at 2.50 or below inplay.
Which is clearly not the case with Winning Warlock's figures.
In any case, not a biggie.