I just switched my Pixel 1 to airplane mode and tried voice input. Sure enough, it worked offline and it was fast! Very impressive work. (I've tried that before, but in the past it could only understand a few special phrases.) I suppose this new feature came with the security update my phone downloaded a few days ago.
There are lots of ways to spin this, but I see it as a significant improvement for any app that could benefit from voice input. It's immediate and not susceptible to network glitches. The benefit for Google, IMHO, is primarily more sales of updated Android devices.
Unless you very recently (meaning today) accepted a download of a new language pack for English, it's likely just the old model, which is perfectly functional, while not being as accurate as the online version.
There are lots of ways to spin this, but I see it as a significant improvement for any app that could benefit from voice input. It's immediate and not susceptible to network glitches. The benefit for Google, IMHO, is primarily more sales of updated Android devices.