No. He could be improving Python on his own time.

For those who didn't catch the reference: https://www.youtube.com/watch?v=ohDB5gbtaEQ

On Microsoft's time, since they are employing him

To be that guy... Didn't Guido officially step down as BDFL?

Yes, he then retired, came out of retirement to work at Microsoft with a remit to work on whatever he wants, and decided the project he wanted to work on was make CPython faster.

What's the title of the budget for employing him? General brain trust? I'm genuinely amused

The title is "Distinguished Engineer".

I have no idea of the pay but based on my research of salaries for getting a job this year I would wildly speculate high 6 digits to low 7 digits.