Question about Sandbox mode (Practice Tool)

So basically, the practice tool is for practicing champions' combos, trying them, looking at their builds, trying out which runes fit them best, right? But as the name - Practice Tool, can't it be so we can play any champ? I don't want to go to PBE or wait for him/her to get on free rotation, can it be so we can play any champ in practice tool?