If BA had not warned cabin crew up front what it intended to do if a strike took place,but had withdrawn staff travel after the industrial action had commenced, then it would be seen as punitive action, but the very fact that staff were warned well in advance meant that they acted in full knowledge of the consequences. Thus it was not punitive but consequential.
BA simply warned them in advance they would be punished for striking. It's still a punishment.
In previous IA throughout the airline for at least 30 years, maybe 40 or more, staff travel has been routinely withdrawn at the start of IA, and always returned with full seniority on agreement. Why should CC have seen this time as any different?