After formal notification, Congress has 21 days to vote to remove the president from office (two-thirds majority required in both House and Senate).
Read it again carefully. He still remains President, but may not discharge the powers and duties. Acting President is not President. Many Vice Presidents have already served as Acting President for short periods of time, able to discharge the powers and duties of the Presidency, but they were not actually President. Even Kamala Harris has done this when Biden was under anesthesia. She is the first woman to have done so, but she is not the first woman President. Even the text of the Amendment continues to refer to the Vice President as Vice President, and the President as President.
Whenever the President transmits to the President pro tempore of the Senate and the Speaker of the House of Representatives his written declaration that he is unable to discharge the powers and duties of his office, and until he transmits to them a written declaration to the contrary, such powers and duties shall be discharged by the Vice President as Acting President.
Virtually impossible for a political tactic...absent stroke or heart attack a lot of Ds would not vote to remove a Prez of their party.