I could see each stint being off for more than 3 weeks would require something from the manager to confirm enough handover has happened. Waiting too 3 weeks is normal each time, but if you’re a project manager and vanish for 5 weeks at a critical part of the project then someone needs to know.

Yeah but why would there be paperwork mandated by law?

I don’t think anyone said they did

The question would then become why a company would impose such paperwork on itself; but someone else replied that it has to do with unions, which I guess could explain it although it's still weird.

Working for a 100 year old 5b/year company the amount of forms to fill in to do various things are extreme.

I could easily see a requirement from high up managment to “reduce risk” by having a department have a plan for an unusually long holiday stint (I.e someone taking 6 weeks off in a row), fundamentally because senior management don’t trust middle management.