Yes, that is correct. What I am trying to tell you is that a passport with JeanLyon’s dates DOES have three months validity when her holiday ends in October 2025, for the purposes of determining her return date. You are still allowed to count “extra” months for that purpose.
What you are not allowed to do is count the extra months for the purposes of entering the EU. So her passport expires for entry in January 2026, and she can’t enter the EU after that date even if the expiry date suggests she has three months left. So no going on holiday in April 2026 on that passport. But it would be absolutely fine to go in October 2025, as the January date is not relevant for determining the date of expiry.
There are TWO independent rules here: one rule about the date of ISSUE and one about the date of EXPIRY. A passport has to be less than 10 years from date of issue to enter the EU. A passport has to have 3 months left before the date of expiry when leaving the EU. They are different rules.