How to set hour format in week timeline with FullCalendar Schedule?

Question

On one version of the full calendar i am able to use this code to change the time format to 2400

slotLabelFormat: function (date: any) {
 if (date.date.minute == 0) {
  return date.date.hour.toString().padStart(2, '0') + '00';
 }
 
 return date.date.minute;
 },

But in this example click week to see how the Day is displayed above the Time as you scroll from left to right: https://fullcalendar.io/docs/timeline-resourceGroupField-demo

When I use the same code I get this result:

The row of days like "Fri 3/1" is replaced by the row of 2400 times, and the row that should have times is empty.

How can I only update the time format while leaving the day row as it was?