My requirements (those given to all WLS for my surgeon/hospital/etc) were no more than 5 grams of sugar or 5 grams of fat if they were any added sugars in the ingredients list. If you've got no sugar listed, it didn't matter what the total was, it was *ONLY* if there was some form of sugar in the ingredients.
It's different for everyone. Even folks on the same diet are going to have different reactions to added sugar amounts. If it works for you, just make sure you go easy on it, you don't want to slowly creep back up, it's easy to go... well, 13 grams was no issue, so 15 shouldn't be... then 15 becomes higher, etc... Not saying it will, just that it could. As soon as you negative a "rule", it doesn't hold the same weight and becomes so much easier to justify.
I'd say, until you are cleared for the "full raw foods", or whatever the last stage you have to be cleared for before you start to venture outside of the prescribed diet restrictions. Just so you've got the full time healing and following their recommendations under your belt and are out of the early stages of healing, just in case there is a problem, if it's on their diet, then it's not your fault if something goes wrong, if that makes sense. Think of it like being under a manufacturers warranty LOL.