Great question. I think you are correct about this.Here is what the Wikipedia says about the fire from the New York Times article:
In 2019, The New York Times Magazine published an investigative article by music journalist Jody Rosen which disclosed that the damage was far more serious than the studio had claimed.
The fire destroyed Building 6197, a warehouse adjoining the King Kong attraction. In addition to more videos, it housed a huge archive of analog audio master tapes belonging to Universal Music Group (UMG).[6] The collection included the master tape catalogues of many labels acquired by UMG, including Chess, Decca, MCA, Geffen, Interscope, A&M, Impulse!, and their subsidiary labels.[6] Estimates of the individual items lost range from 118,000 to 175,000 album and 45 rpm single master tapes, phonograph master discs, lacquers and acetates, as well as all the documentation contained in the tape boxes.[6] Many tapes contained unreleased recordings such as outtakes, alternative versions of released material, and instrumental "submaster" multitracks created for dubbing and mixdown. Randy Aronson, manager of the vault at the time, estimates that the masters of as many as 500,000 individual songs were lost.[6]
Among the losses were the entire AVI Records catalog, all of Decca's masters from the 1930s to the 1950s, most of the original Chess masters which included artists such as Chuck Berry, Muddy Waters and Howlin' Wolf, as well as most of John Coltrane's master tapes from his later career on Impulse! Records. On Twitter, Rosen stated that the Coltrane masters were among the most checked-out Impulse! items in the vault, and a source had told him that the masters for A Love Supreme were likely elsewhere during the fire.[13]