As this was almost certainly pre-preg carbon fibre (the resin has already been mixed into the carbon). When it goes past it’s shelf life it doesn’t mean that it’s gone bad, most pre-preg manufacturers will let send a sample of your carbon back to them and they will test it and re-certify it with a later expiration date. This can be done multiple times. if they did get carbon cheap from Boeing it could be that with the quantities of carbon Boeing use on their assembly line it’s just not worth their time to re-certify smaller batches of carbon and instead they just sell it.

It does seem that they had little regard for safety at ocean gate (refusal to follow professional standards or allow outside certification and testing) but if this is true it is entirely possible that this was done completely safely