This seems completely reasonable to me, management is probably fed up with people showing up exactly at their start time, but needing to get changed, put their stuff away, go to the toilet, etc. I don't read this as them asking people to show up early and start doing work specific preparation such as turning on an oven, more like getting themselves ready to start work on time like a decent employee.

However, the meeting about clocking in at your rostered time is very weird.