How does Floating Bar Chart gets it's data?

[Udemology]

I am trying to do some custom data structures but I notice this is not fully working as I thought it would.

With Floating bar chart if you assign

data: [1, 2] // >> gives a floating bar/ Works.

An other version also works with data structures

data: {
   x: today,
   start: 1,
   ending: 1.50,
   startAndEnd: [1, 1.50] 
}

options: {
  parsing: {
    xAxisKey: [startAndEnd],  // >> This works
  }
}

But if I would have this and use data structures it would not work:

data: {
   x: today,
   start: 1,
   ending: 1.50,
}

options: {
  parsing: {
    xAxisKey: [start, end],  // >> Does not work as expected, only grabs the first value. Does not float. 
  }
}

Is there a reason why it does not recognize the array? I hope there is some insight on how this works.