Because they now scale to CP160.
All potions now scale up to the player, as long as they are in the original range of the potion. For example, an L10 potion will scale up to L19 with the player. But to get L20 you have to make that tier of potion.
Well, it use to be that if you made a Vet 10 potion, it would be Vet 10 level all the way to Vet15 or for a while, Vet16. So, it's better now that they scale in the range.
The tool tip on the completed potion tells you the scaling range. However your still using a CP150 Solvent to make the potion, so that is why it says CP150 potions. The Solvents don't scale, only the completed product does.
BTW, its the same now for Foods and Drinks.