[Xaccers]

If the contract asks for something but doesn't say it has to work, then you won't get the manufacturers pointing this out, they just want to be paid and know they'll be able to charge extra to get it fixed.
Happens all the time.
One company I worked for had their finance director write the spec for some software as he thought he was the bees knees.
Of course the software was to spec but wasnt expandable in a way we'd want it to be (an obvious way)
His attitude was "why didn't they write it to do that?"
Simple, because they knew they had him by the balls, either he pays them the extra, or he starts from scratch and gets another company to do it costing even more.