Except that it's actually not. If you have the whole inventory client side, you can search it in memory, locally, with no network IO at all. Nothing will be faster than that.
If you only actually needed one item client side, a search would be faster than retrieving the whole inventory, yes. But inventory is used so often that it doesn't make sense to do that 80 times when you could sync the whole thing on login and then do things locally (and send update events to the server). When something is needed so frequently, it becomes more efficient to eager load it and cache it than it does to load it on demand every time you need it.
Higher tier nodes often penalize you if you only have 600 GP, like the 70 one star nodes IIRC need at least 650 to have any HQ chance whatsoever.