Threadomancy here.
But since it's back from Mandos, I would approach this, as I tend to do, externally: the chapter "The Shadow of the Past" (originally "Ancient History") was one of the earliest written, and although subsequently emended Tolkien wasn't doing so with a fine-tooth comb; moreover, much of the history of the Great Rings (especially the Three) didn't arise until the Appendices, written well after the main narrative and, although Tolkien did attempt some revisions to square things up, this was done in a tearing hurry during the rush to publication 1954-55.
Besides, both Tolkien and his loremaster alter egos (Gandalf, Elrond and Faramir) tend to speak in sweeping generalities which aren't necessarily precise to three decimal places.
Is Treebeard or Bombadil the "oldest living thing?" If Gandalf thought it important, he could have added a verbal footnote with all the fine print on Great Ring ownership.
"Ring use may be habit-forming. Gwaith-i-Mirdain Ltd disclaim all liability for damages direct or indirect associated with Ringbearing. All Rings non-transferable (except the Three Rings and/or if the bearer is an Elf, or in accordance with Subparagraph 17(g)(1) 'Dwarf-Lords and their Heirs.' Batteries not included."