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I don't think it's a joke, since this seems like a pretty common case of overnegation.
And they also guard against the risk that the taxpayer does not bear a disproportionate burden of the costs cleaning up the banks. overnegation, comments that "My fear is that they actually mean exactly what they say."
On the other hand, the exclusion could have been grafted onto the easy version, for emphasis: overnegation.
At least twice here on Language Log, we've looked at combinations of negation and exclusion that might be seen as overnegation
In case 1, "but less than precise" might have been intended as emphatic; that would be routine overnegation, with an exclusion phrase in addition to an external negative.