Assuming, for the sake of discussion, that the documentary is not making wild or exaggerated claims. In that case it can depend, can you give us a few examples? Depending on the context, it could be the first time in many decades researchers have been allowed to examine a particular mummy with modern equipment. Or it could be the first time that a particular place or object is been studied with a particular goal in mind, looking for clues that might support a certain theory.

When Egyptologists make a discovery, the artifacts or location discovered is carefully photographed. Careful notes are made on where and how the item was found, in what condition it was found, measurements are taken, depending on the nature of the discovery, samples of organic matter may be taken. Most excavations unfold one painstaking stage at a time. For example beads may be photographed when they are first found embedded in the dirt, with the workers noticing if the pattern suggests they may have originally formed a necklace. The beads would be photographed again when they are removed from the site and cleaned, perhaps measured at this point, or photographed next to a color chart for future reference. Then photographed once more when the necklace has been reconstructed and the beads are laid out elegantly beneath a glass case as part of a museum exhibit.

The information gathered during this process will eventually be entered into a permanent record as a monthly or annual field report of the archaeological team's activities. These are usually not read by laymen, with their titles like Waseda University Excavations at North Saqqara: A Preliminary Report on the Fourth to Sixth Seasons, August 1995-September 1997 they can strike most people as a bit dry, but they can form the basis for an article, of the peer reviewed, academic sort, like the ones in the Journal of Egyptian Archaeology or even a book, if someone thought something particularly noteworthy was found.

Now keep in mind that all this information would be available to others in the field who might never have set foot near the dig. So if they draw upon this research and come to the conclusion that this makes their theory concerning say, the unknown identity of a (presumably) royal mummy, worth revisiting, and justifies running certain tests, or revisiting an archaeological site not open to the public, and are granted permission to do so, then yes, the documentary can truthfully say "For the first time...archaeologists will probe the darkness of the forgotten to tomb to discover if it belonged to the sun king's long lost sister!" That said, as I mentioned earlier, documentaries can and do make exaggerated or completely unfounded claims. The quality can vary depending on who's making the show, the remarks of academics can be taken out of context and used to to "support" the theme of a show, while TV producers, though they may be acting in good faith, don't have the expertise to assess the historical information they're dealing with.

A few years ago there was quite bit of controversy when British Egyptologist Joann Fletcher claimed she had identified a mummy as being that of Queen Nefertiti, she wrote a book on the subject and a popular documentary aired around the same time. More recently Nicholas Reeves has cautiously suggested that a wall in Tutankhamon's tomb may conceal an entrance to a second tomb, perhaps housing Nefertiti or another relative.