What constitutes an "extraordinary" level in "extraordinary claims" is one the least-defined things in aphorisms related to science. It reminds me of what some call the "stages of change" First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident.

It seems if what is "extraordinarily" unlikely can easily become "true and self-evident" then extraordinary was a more a way of fighting against things opposed for more emotional than evidentiary reasons.