Same. I run a small business that employs about 15 people. Our sickness policy is that you get up to 20 days paid sick per year, but if you have more than 7 days off in a row you have to provide a certificate from the doctor.
Normally this isn't an issue at all - we accept that everyone is sick sometimes. Covid has actually helped reduce our normal incidences of illness as people are a bit more hygience conscious, not in the office so much, and WFH if they are ill.
We have one member of staff, however, who used all his 20 days sick last year, all his annual leave AND had more unpaid sick days (as he always returned just before the SSP would have kicked in as that would have required a doctor's note). Overall he was out of the office for in excess of 10 weeks. He also proved very unreliable in WFH so he's now entirely office based.
He knows the terms of our contracts inside and out so always plays safe just within the requirements. He is often ill, but it's because he has a huge social life outside of work and burns the candle at both ends. I'm fairly certain he takes the piss too and is more than capable of working, but chooses not too.
We have previously taken disciplinary action against him and he's on a final written warning, so he's keeping rigidly to the terms, but it's massively frustrating as an employer. We won't allow one person's poor behaviour to ruin it for everyone else, but I can see why some employers aren't as generous with their sick pay as we are.
OP's "boss" is massively unreasonable, of course, and I'm glad you've got stinky farts in the office today!
Good luck with the job hunting!