It is an older paper, though that in itself isn't a reason to discount this (or any science). For example, the DoE still uses an 2014 predictive model to estimate longevity of today's EV batteries at "12 to 15 years in moderate climates (8 to 12 years in extreme climates)" [1]. However as the DoE says, battery longevity depends on a bunch of factors e.g. chemistry, charging patterns, etc.

To the practical matter - yes, EV manufacturers are very careful with warranty periods. Anecdotally, an acquaintance had a Tesla for 8 years. 6 months after the 8-year battery warranty expired the battery ceased working. The details were a little unclear (it was explained in broken English/Norwegian). That said, anecdata carries little weight. What we need is more peer-reviewed research to update our understanding of battery longevity. Until we have that we need to rely on the existing published knowledge... otherwise anyone can assert anything and we learn nothing.

[1]: https://web.archive.org/web/20250530000446/https://afdc.ener...