I spent a good part of a year working specifically with the Bluetooth GATT spec designing my own client and servers which would try to function as close to the spec as possible.

The spec is very bad, I'm sorry but I understand the amount of effort that must have gone into building it. There are blatant holes in the entire spec, documents are broken apart in some chaotic pattern where to implement a single ATT you need to reference 3 documents simultaneously(almost).

The documents have broken links or just flat out incorrect links. Worst part is, a lot of device manufacturers just yeet the GATT out the window and have custom UUIDs with custom everything which you'll never be able to implement properly with reverse engineering it.

Idk I think the spec is a good initiative marred by execution