Seems he took unpaid leave, rather than claiming illness when that would have been a lie.
As for "an employer should try to make adjustments to the job if that's possible" I can only confirm that (with care) that can be a route to ending someone's position.
One of the teachers at my sister's school (when she was a head, prior to her retirement) was off for weeks at a time, would return for a week or two and then be off again. Was costing a small fortune in replacement staff (covered by insurance, but premiums don't go down after claims!).
After months of this, my sister had to review the situation, inviting the teacher (and union rep/ husband if preferred) to a meeting. Eventually ended with the teacher going, as she simply wasn't 'capable' after all the encouragement and assistance (back 1 day a week for a month, then 2 days, etc).
She was insistent to the end that she wanted the job, but her husband and union rep could see how my sister was unable to keep her on, given the uncertainty of whether she would be at work or not for any length of time, and her pupils were the ones most affected by this disruption.
Think for a big firm they have a pretty poor attitude. It would be worth "demanding" (if requesting fails) written policy on coming in with D+V, and situation if HA man became ill. No fun for HA man, and not sure whether firm would be culpable if staff in fear of being off sick even if they have something contagious.
It just does not make sense to go in (glad he went home - was he sent home?)