The 25th is not a magic wand to remove Biden. If he doesn’t want to go, it is actually easier to impeach and remove him than it is to remove him via the 25th.
Yes, it’s odd. As you noted, it’s actually more difficult and complicated to remove a president by the 25A than by impeachment.
But the 25A does have one advantage. It can *temporarily* remove a president rather quickly. If the VP and a majority of the cabinet agree, the president is out and the VP is the acting president. Congress isn’t even involved.
But to keep the president out, that’s when it gets messy. And then Congress is involved.