Well, the previous wording would more likely be read as it setting the reach to 10 feet, then adding the +5 per 10 levels to that, and completely ignoring the base reach of the creature. This wording makes it more clear that it is in addition to ones default reach. If you wanted to be really thorough, you could add something in parentheses noting that for a creature with 5 feet of reach it results in 15 feet total (but better worded).