There are people who want the RN to go back to CTOL aircraft, & carriers with catapults. Some see it as the only way to protect the FAA from the RAF, others are convinced that it's necessary if we're to be taken seriously as a proper aircraft-carrier-owning country, some just like the idea. Some of these people grasp at every straw, looking for indications that their dream is about to come true. Any hint of a change to plans is leapt upon by them as an opportunity. Therefore, the suggestion that the UK & France were considering closer co-operation, including in naval matters, was seen by some as a possible signal that carrier sharing was on the table, largely because that's what they'd like to hear. Co-operation would necessitate RN carriers with catapults, as that's what France already has. You see?
Thus, stories about carrier sharing start to spread, not because of evidence, but because substantial numbers of people would like it to be true. The media reacts to gossip, & therefore reports it.