You can not (simply) view the content in the clipboard from your mp3tag copy-step.
I assume that you still are in doubt if the removal of your unwanted lyrics works
Why would you change the number of selected files between the copy & and the paste step in this case?
Maybe it helps if you compare this copy&paste step with the c&p in Microsoft Excel:
a) You select one ore more complete Excel rows
b) You press CTRL + C to copy the content of this Excel rows
c) You select the new target
(which can be the same rows, some new empty rows or some overlapping rows)
d) You press CTRL + V to paste the content of the copied rows