It was just a scientific name, the scientists were waiting to see if another specimen would show up so they could analyze it and properly give it a name. That didn't end up happening, but the creature did get named eventually. Aside from inaccurately and preemptively trying to name, there wasn't anything else the scientists could have done.
No, the scientific inquiry towards this species was not proper. One main purpose of taxonomy in scientific research is to identify ancestries of living species and how interconnected they are regarding evolution and appropriation of new characteristics. Naming species, where they are near extinction or prosperous, serves to develop this valuable field of categorization. The Giant Tortoise should have received its name the moment it was deemed a separate species from other similar turtles.
Giant Tortoise had not received classification for over 300 years. Upon discovery, the tortoise should have been collected and cataloged for classification. Instead they were eaten. If it was known that the Giant Tortoise would be hard to collect they should have been either separated or kept from being eaten.
I have no problem with turtles being eaten but if it is a rare species that has not even been named yet, then there is certainly something wrong with the scientific process. This is a bit of a disgrace quite frankly and should never have happened in the scientific community.