A survey of scholarship on the amendment found no specific threshold – medical or otherwise – for the "inability" contemplated in Section 4. The framers specifically rejected any definition of the term, prioritizing flexibility. Those implementing Section 4 should focus on whether – in an objective sense taking all of the circumstances into account – the President is "unable to discharge the powers and duties" of the office. The amendment does not require that any particular type or amount of evidence be submitted to determine that the President is unable to perform his duties. While the framers did imagine that medical evidence would be helpful to the determination of whether the President is unable, neither medical expertise nor diagnosis is required for a determination of inability ... To be sure, foremost in [the minds of the framers] was a physical or mental impairment. But the text of Section 4 sets forth a flexible standard intentionally designed to apply to a wide variety of unforeseen emergencies.[4]: 7,20 https://en.wikipedia.org/wiki/Twenty-fifth_Amendment_to_the_United_States_Constitution
But, as long as Joe can sign two letters, one to the Speaker of the House and the other to the President Pro-Tempore of the Senate, requesting to be reinstated, he is back as POTUS. The next action to remove him would be a 2/3rds vote to remove in both the House and Senate - a higher threshold than impeachment.
If he is stroked out in a coma in a hospital, then he cannot sign these letters. That is what I think the framers of the 25th Amendment had in mind. Or, zoned out and incapable of signing his name.
Biden has angry dementia and will resist all attempts to remove him.
Frankly, I would rather run Trump against Biden than Trump against any other D. Yesterday’s double standard of prosecution discretion just helps Trump. Given this, I would advocate that the Republicans do not vote to remove Joe if given the chance. Deny them the 2/3rds. It is only until 1/20/2025 (about 10 months).
All IMHO.