If the stats of an item level were to match the stats of an actual player level, then the effect of each point in STR/DEX/INT etc. would have to be significantly higher (x3 or x4) than what we have right now. iLvl90 items were designed to be coil-equivalent for that reason, so if they drop Allagan gear down to iLvl65 then the current stats on the item would be reduced as result, and the overall effectiveness of each point in stats would have to be boosted by 3 folds. Think about materia, each +1 stat point materia would render a piece of gear jump in item level in theory, unless they reduce the materia down to +0.1 to +0.5 each... but then again, what is the point of that?