I've known this is your understanding for a long time. The problem
seems to be either that people can't see how flexibility and
uncancelability are not mutally exclusive, ...
The words are mutually exclusive on the logical level. If something
cannot be cancelled, that implies no flexibility. If there is
flexibility, it means that the something can be cancelled. And Rolf has
made it clear many times that by "uncancellable" he does not mean "only
rarely cancelled". It is he who is insisting that there is no
flexibility here, so that one counter example which is not an
arbitrarily defined "special usage" is enough to disprove an alternative
hypothesis.