I think that's extremely unlikely in the case of Oxygene 7–13 ... it's only from 1997 and any digital audio format from then is still easily supported today.
With early 80s digital tape formats (or indeed experimental 1970s ones), where you had a few pioneering manufacturers (3M, Mitsubishi, Sony...) bringing out digital multitrack machines, it can be difficult to get a vintage machine to play these back on, but this is Jarre we're talking about here! Sourcing vintage machines is what he does
Pixar animation isn't really comparable - there you're talking about the actual animation software, all we're talking about here is the recording digital audio onto tape or hard drive, it was nearly always in the same underlying PCM format.
No, this whole "remastered from the original analog tapes" thing is just a bullshit marketing phrase, that some idiot in a suit thought would help sell more CDs, even though it's patently ridiculous and untrue.