That sounds like your place of work is significantly over staffed.
Its not actually. It is adequately staffed but not over-staffed. You cannot plausibly read anything into the previous comment and come to an assumption of over-staffing.
I'm sure you are more than aware of contingency planning? priortising? scheduling etc, just part of the normal course of business organisation.
The industrial action was in advance notice. Management set about minimising disruption to services and prioristing scheduled payments to their customers, which as I understand, there has been no reported disruption.
Customers with scheduled appointments were notified in advance and either given an alternative date or requested to contact offices to re-schedule, again depending on the nature of the appointment priority was afforded to serious cases over cases with less urgency. This is disruption but it was minimised to greatest reasonable extent.
Disruption was caused to those that intended to walk-in call to offices that day but with no prior notification. How disruptive it was for them is unknown.
Where I work it is not public facing. Like most well run organistions priority was given to tasks considered more critical and time-urgent and tasks considered not critical were addressed over the coming days as time and capacity allowed.
All normal routine stuff for business operations.