I would argue that shipping to a limited test group qualifies in terms of measuring velocity, which is what the OP said they were impressed with.

Launching to 10000 people vs 10000000 is a matter of scale (which is still important, but not the same thing as), not velocity.

I think there are really three stages here when developing at a megacorp:

1) Prototype that works on a single dev machine

2) Test version for 10K people

3) Worldwide rollout for 100M people

All three are velocity, and all three are difficult. Especially for something so server resource intensive as this, going from 2 to 3 may require even work than getting just to 1, or from 1 to 2.

There's no reason to treat scale as something different from velocity. At the end of the day, your feature doesn't exist until it's rolled out worldwide, so working on scale is no different from any other work on building the feature.

i didn't see a place where they said they had 10k users already

Microsoft employs somewhere above 200k people. 10k is only a 5% internal rollout. That seems entirely doable without any fanfare.

The numbers are also completely made up, used to illustrate the point. Launching a product to X users is different than scaling up to X*1000 users, if that makes you feel better.

There's no reason to believe that what they're testing right now has any relation to what they show in the video.

FWIIW, This seems rather similar to Github Copilot in VS Code. Been using it for a year, training data issues aside the product is absurdly good at times.