I'd actually point at the other half of the title than the existing comment when being pedantic "Replacing [...] with a 64-Bit Word" isn't quite right, it was replaced with a manually packed 64-Bit Word and the occasional heap allocation.

I'm not sure being this pedantic is particularly useful in titles though...

It's worth calling out either way. It's not just an encoding scheme, it's a reasonably significant change in architecture.