Booster requirement and Johnson & Johnson/Janssen vaccine

[Colleen27]

We're heading to Europe in June, so I'm working on clarifying the various countries' vaccine requirements to make sure everyone on this extended family trip has what they need, and I noticed this in the French rules:

Since 1 February 2022, people aged 18 or over who wish to enter French territory must have received a booster dose of an mRNA vaccine no later than 9 months after the last required dose to be considered fully vaccinated.

Is this accurate? My husband's primary and booster doses were both the Johnson & Johnson. Do I need to arrange for him to have a dose of one of the mRNA vaccines as a(nother) booster for the purposes of travel if he decides to catch up with us while we're still in Paris? Or is there a separate rule on the J&J/Janssen vaccine that I'm not seeing reported in the sources I'm looking at?