What do you suggest the company do?
How does a company deal with workers who belong to a union? That depends on so many things -- the history, the locality, the business, the workers and managment themselves. There can be a lot of reactionary dynamics from nearby unions and culture not directly in the employer and worker's union.
I can give no specific suggestion to the company -- short of a general suggestion to get smarter -- this nanny-policy is dumb and counter-productive for reason mentioned.
I read their absentism rate is over 10%. I can't blame the company for wanting to crack down on them. But is this the correct way?