Airworthiness is a sub element of System Safety
As has been intimated the theoretical airworthy aircraft is nought but a (un)controlled ballistic missile if the crew are not competent for task and that definition must include a measure of currency. Some of the more gifted and talented may be able to maintain competency with ease and others need much more stick time.
The overall safety case, that raises the questions that need to be answered to assure system safety, should have considered the possible outcomes and attendant risks arising from reducing flying hours. It would appear that it did not.
It is the appetite to address and manage this risk especially the frequent updates that are required to the safety case, including the career moments that may come with raising objections/observations, that need to be reasserted.
Not a pilot so can only trust opinions that 10 hrs per month is woeful but I know that as a motorbiker I need to get my eye in after some time out of the saddle, anything else is inviting disaster.
SJ