I've only ever used Silca, and for the last couple of years that's been Silca with the Endurance Chip additive, which makes the wax 'harder'. Possibly MSW starts off, or just is, 'softer' than Silca wax? If it is, then the chain would be quieter from the outset. My chains are really pretty stiff, post-waxing, with minimal lateral movement and very stiff articulation in the normal direction. I'd assumed this was normal for all waxes, but very possibly not. I've actually heard people who use the Silca Speed Chip, which makes it softer, say that the drivetrain is immediately quieter.
Whatever the reason, it sounds like a good result for you :-)