Well, by that logic, perhaps if Stron or T'Mir were still alive perhaps one of them should have been appointed to the position. They lived with them for months. Few Vulcans would've had more experience with humans.
But that was clandestine experience that the Vulcans preferred not to let the humans know about. The crew who made first contact in 2063 would've had the first
overt experience interacting with humans. They would've been familiar to the people of Earth. There would've been a two-way relationship established in that contact, and that's something that can be built on in establishing diplomatic ties.
And of course, it should go without saying that such familiarity is only one of the many factors that would be weighed in appointing an ambassador. Logically, you'd want someone who's trained as a diplomat. T'Mir, Stron, and Mestral were the crew of a
clandestine observation ship. The people who selected the crew for that mission would not have expected them to interact with aliens directly and thus would not have chosen personnel with diplomatic qualifications. But if that Vulcan starship crew in 2063 decided they were qualified to make first contact themselves rather than calling home for reinforcements, it follows that such contacts were part of their existing mission parameters (since the Vulcans are a very by-the-book people, especially at that time), and thus it's a reasonable expectation that the captain of such a ship -- or the first officer, or whoever it was that made the first contact --
would have diplomatic training, and would thus be a more viable candidate for the post of ambassador than T'Mir or Stron.
Of course I'm not saying that Solkar
had to be that particular Vulcan. But I see no reason to consider it impossible or unlikely. There are valid reasons why that particular individual could've been appointed the first Vulcan ambassador to Earth, and thus it's a legitimate possibility that he was Solkar.
