Ablative paints wear off with the flow of the water. If you hose or powerwash the bottom, you'll see the ablative paint coming off. Hard paints only come off with sanding or blasting.
The ablative paints are great in terms of keeping layers of old paint off the bottom. This makes it easier to keep the bottom smooth, free of the "craters" that flaking old paint leave behind. A light sanding before recoating is all you need.
BTW, I've been using E paint ablative with great results.
Hope this helps.