FullCalendar : No header for timeGridWeek outside ValidRange

I'm using fullcalendar 5.5.0 with Angular 10.

Something kind of annoying appears during the migration (fullcalendar v4 -> v5), there is no longer a header for the date before the start of the validRange :

With the parameters :

    initialView: "timeGridWeek",
    validRange: {
      start: "2021-01-22",
      end: "2022-01-01"
    },

Adding a visibleRange doesn't change anything.

Well, it will save my day if someone know if it's a known bug, (or a feature), and how to fix this without adding custom code and .revert() to any action on event (move, resize, ...).

Thanks !

PS: you can easily try it here : https://codesandbox.io/s/kind-hertz-x4etl?file=/src/app/app.component.ts