>>> I think the following is problematic:
>>>
>>>    (defun tab-line-switch-to-prev-tab (&optional event)
>>>      "Switch to the previous tab's buffer.
>>>    Its effect is the same as using the `previous-buffer' command
>>>    (\\[previous-buffer])."
>>>
>>> If the "previous tab" does not show the buffer 'switch-to-prev-buffer'
>>> would switch to, then the doc is wrong.  I'm not sure whether
>>> 'tab-line-tabs-window-buffers' can guarantee that this chooses the same
>>> buffer 'switch-to-prev-buffer' would switch to, though.  If it doesn't,
>>> then the effect should be that of C-x b switching to a buffer earlier
>>> shown in that window.  BTW, burying a buffer removes it from the tab
>>> line but does not prevent 'switch-to-prev-buffer' from switching to it -
>>> it just makes it very unlikely IIRC.
>>
>> tab-line-switch-to-prev-tab doesn't choose buffers itself:
>> for tab-line-tabs-window-buffers it just delegates the task
>> to switch-to-prev-buffer.
>
> But what is the "previous tab"?  IIUC it is the one on the left of the
> current tab in the tab line.  But that tab is not necessarily the one
> 'switch-to-prev-buffer' will switch to.

It's the same tab buffer that 'switch-to-prev-buffer' will switch to,
while using tab-line-tabs-window-buffers that is the default behavior.

So here are changes in the documentation that explain this: