[Big Sur (and later)] What's the purpose of the apparently useless 20-pixel gap at the bottom of NSTableView?

Optimal height = height that displays all the rows such that you can't scroll the tableview vertically (assuming elasticity is set to none).

On macOS Catalina and earlier, the optimal height for a headerless NSTableView is:

number of rows * (height of row + height of intercell spacing)

On macOS Big Sur and later, it looks like to be:

number of rows * (height of row + height of intercell spacing) + 20

[Q] Why do we have to add an apparently pointless 20-pixel high white space at the bottom of the NSTableView in macOS Big Sur and later?

This is rather annoying and breaks controls/views spacing.

[Big Sur (and later)] What's the purpose of the apparently useless 20-pixel gap at the bottom of NSTableView?
 
 
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