The fact that a bank may come up with a reason to dishonor a check does not mean “[n]o bank is ever obliged to honor any check, and when they do, it is just a courtesy to their accountholder”, which is what you claimed.
“As provided by law” means everything, because the staleness of a check and the bank’s right to dishonor a stale check are provided by statute (except possibly in Canada).
My guess is that it’s not because the check is “stale,” but because the class action folks set up a dedicated account for payouts, and the court (or parties) specified what would happen to money unclaimed after a period of time and after that amount of time, the money went away per the settlement agreement.
Like **Mops **said.
There is no statute that compels a bank to honor a check, if they can present a plausible reason for declining to do so, and the bank has very wide latitude to protect its own interests where there is doubt. A bank has full discretion, for example, to evaluate the apparent genuineness of the signatures. Or if it appears to be altered. Or has any ambiguous information on it. Or has been folded, stapled, spindled or mutilated. The list goes on. The mere fact that the check is spit out by a machine reader or processor is sufficient reason to decline to honor it.
Even assuming your first premise is correct (which it isn’t), your original statement is still untrue.
Update: I had a message from Collectiva this morning. As suggested, the monetary compensation expired after six months. She apologized but said there was nothing she could do. I’ll dig up the paperwork to see if this was mentioned for curiosities sake.
At least my bank didn’t charge me a fee for the returned item!