Yes, very important points that the US group is not an official governmental delengation. Much like the family of the missing French women are not official, and are also displeased that the French government cannot just send over some of their SAR people to a foreign country and usurp the responsibilities and domain of the host government.I think they can't be disclosed to third parties, like the media, not the Greek police. The US rescue team most likely didn't come with an official request, they were just volunteers so they they can't be privy to all the inner workings of the investigation.
Same thing is being said about the 19 year old UK kid missing on Tenerife. The UK is just not going to send a delegation to look for them in Spanish territory.
Just like Greece would not send a delegation of searchers to the US to look for a missing Greek citizen, without some special request from US LEO.