You are wrong. Development fees are for clubs who have developed a player and they leave on a precontract. It was designed to protect smaller clubs having their players tapped for $#@! all.
As long as Celtic offer him a new deal, we will owe them money based on various costs and how many years he's been at Celtic.
Mentioned in the other thread it might be that it only works if he's offered an improved deal by Celtic, so in a freak scenario, we might get a situation where his current deal at Celtic is pretty sweet, so an improved offer by them might not be in their interests just in case he accepted it. So maybe they pass and lose out on the money.
Also. We won't be the only club able to offer a contract, Celtic might try forcing a sale elsewhere in January and an immediate move elsewhere might suit him better as he'll want to play football not wait another 7 months.
Or, Celtic have problems, he gets game time, impresses and becomes more regular... Could screw us again.
You cannot begin to be certain this will happen on a precontract. Nobody could even begin to know at this stage. Not hibs, not Liam, not his representatives, not celtic.