The Rambam also has ” vedamo shachor” (citation eludes me), though in treifos, Rashi and Tos make “ukma” “k’kuchla” to differentiate form kediuta (ink black).
As posted by Y.T. in the old techeles thread, techeles is referenced (citation in old thread) as nignaz. So the great palette (npi) of sources on techeles is not a “how to find it” manual. No one, other than the replacement experts at the Temple Institute, has gone looking for the Aron, the hatzosros, the ketores, or the nechash hanechoshet.
Tangential to the safek esrog, I have cut open large selections of esrogim, with sample batches from different pardessim, and roughly one in thirty present with a full fruit center, i.e. murkav. One has to say that there is either a latent murkav gene in many strains from past parentage , or there is “murkav bidey shamayim, by cross pollination. Food for thought this comming Succos.