Yeah, I remember this. But I think it was just Samsung that made this blunder, no?

NVIDIA had a much funnier (infuriating) one, where Tegra X1 had caches between the big and little cores that weren't always coherent. Their solution was to just turn off the little cores while continuing to spew marketing bullshit about it being an 8-core chipset.

Yes, you look to be right that the Samsung-designed Mongoose core in the Exynos SoC had 128-bytes cache line size, while ARM designed their generic Big cores to also use 64-bytes like their Little cores. Still though, seems like ARM did not provide guidance that these specs must match between Big & Little cores, and Samsung also didn't catch this either.