Anybody used FAM to dispose an asset? Not sure why even though on the asset, the disposal cost account is populated with a disposals account, at point of write off, it credits additions, debits depreciation? I'd expect disposals?

I believe that only gets triggered if your asset has a non-zero value. Assuming it does, it's basically "worthless" since you've already taken the whole cost as expense. So the entry just takes the asset and accumulated deprecation off your books.