I think what it means is that the recommendations and limitations in regard to where to place transmitting aerials needs to be considered rather more carefully than was the case not very many years ago.
Within this forum, but back in about 2015 or thereabouts I wrote about the difficulties I faced in regard to where I should place the transmitting aerial for a new Class B AIS instrument that I had fitted onboard my boat, and where the manufacturers recommendations regarding the horizontal distance away from humans and the vertical separation between the base of the transmitting aerial and head height etc., meant that the transmitting aerial could not easily be sited within the confines of the aft cockpit area of my boat. The only possibility for placing a transmitting aerial within an aft cockpit area meant placing it on top of a fairly high structure that I did not have. The end result at that time in order to avoid radio transmissions from possibly being harmful to anyone onboard my boat, was to buy and fit an aerial splitter device so that my VHF transmitting aerial located at the mast head could be used for both the main VHF transmitter, and for the AIS transmissions.
From some of the discussions at that time, it was evident that there were a number of us who felt that following the manufacturers recommendations in order to avoid a situation that might cause harm to others, was probably going a bit over the top, and was frequently ignored with transmitting aerials smply being placed on pushpit handrails. Now it would seem to me that there is to be some kind of clamp down on the installation of transmitting aerials to ensure that no innocent bystander can be harmed by radio transmissions from aerials that have not been placed in accordance with official recommendations.
For what its worth, I was not overly happy with the aerial splitting arrangement, several times the AIS instrument would post up a warning of “High VSWR,” (whatever that means) and where possibly and because of which, I felt that the performance of the main VHF radio was compromised.