Looking at the documentation for a floating label of a textarea, https://getbootstrap.com/docs/5.0/forms/floating-labels/, it appears that the label overlaps with the input if the content is scrollable:
Is there a way to prevent this and make the scrollable area below the label?


It's a known issue of Bootstrap 5: #32800.
What I have done is a small hack until they fix this bug.
Basically I put a pseudo element between the textarea and label with a white background color.