He is not going to pay us what he owes us? I highly doubt ARS would do that...
This is a problem with SMPPS, not the pool op being a crook.
Yes and no. It's a problem with him apparently giving people the impression that it was owed in the first place.
To be fair, your page about SMPPS doesn't say that "extra credit" isn't guaranteed and may be lost if the pool stops mining with a negative buffer, either.
No, it doesn't, but Luke-jr has been at pains to mention it when it crops up from time to time, and once in this thread a few pages back. I don't think it's been left unclear on purpose, and if you read the explanation knowing that "extra credit" is not guaranteed you'll notice it is actually there:
The difference between a miner's actual (SMPPS) earnings and PPS earnings is retained as "extra credit", and considered in future blocks.
I agree that making it clearer would be useful - perhaps adding "and is not guaranteed" at the end there might help.