Note that almost all tests and marketing claims about M-DISC (most notably the 1000-year claim) where about the DVD versions. The main distinguishing characteristic of DVD M-DISC is that they do not use organic dyes like standard DVD+/-R, which can degrade relatively quickly. This is also why M-DISC DVD is not always compatible with any DVD reader/writer.

Verbatim / Millenniata loves to conflate claims about the original DVD M-DISC and the later BD-R M-DISC. But unlike DVD-R, standard BD-R already don't use organic dyes (with the exception of some low grade "LTH" discs). AFAIK there has never been good evidence that the BD-R M-DISCs have any special sauce compared to any other non-M-DISC BD-R. (Strengthened by the fact that there have never been compatibility issues or special equipment requirements to read/write M-DISC BD-R.)