Here is the finding in full, so it can be checked rather than taken on trust.
A Nusa Penida freediving school publishes a survey of the country's freediving destinations at freedivenusa.com. It names ten: Nusa Penida, Komodo, Raja Ampat, Alor, Sumbawa, Maratua, Morotai, Wakatobi, Bunaken and Biak. The Indonesia page of the dive-travel guide DiveJourney names nine regions: Tulamben and Amed, Nusa Penida, Raja Ampat, Komodo, Bunaken and Manado, Derawan, the Gili Islands, the Togean Islands, and Padangbai and Candidasa. FreediveMap's Indonesia directory files everything under Bali, Lombok and Aceh, with Amed, the three Gilis and Pulau Weh as its locations. Three further guides — Dijiwa Sanctuaries, The Broke Backpacker and The Salt Sirens — are scoped to Bali and its neighbouring islands.
Tanjung Bira appears in none of the six.
The honest reading of that has three parts. First, the three Bali-scoped guides prove very little about Sulawesi: a Bali list omitting a Sulawesi cape is doing its job. Second, Sulawesi as a whole is not being ignored — Bunaken in the north, Wakatobi in the south-east and the Togean Islands in the centre are each named in the wider guides. It is specifically this corner of the island that does not turn up. Third, the guides that range beyond Bali range a long way: the freedivenusa.com survey reaches Morotai, "tucked away in North Maluku", and Biak, "in West Papua". Remoteness alone is therefore not what keeps this corner of Sulawesi off them. What does is not something this page can answer.
Being absent from a list is not a quality signal in either direction. What it does affect is how much you will be able to research before you arrive: coming to South Sulawesi means going in with less information than you would have for Amed.