Yes, I would be surprised.

What big tech company makes it easy for you to take code written and deployed there while you were employed, and just open-source it?

I know there are big tech firms that own everything you do outside of work, but have a fairly easy process to allow you to release that as open-source.

But this is different, this is about code written for and deployed by the company itself, that isn't part of any corporate open-source strategy.

Story time. In a past life, I tried to open source code I wrote at work. My manager greenlit it, but obviously that wasn't enough. Next thing I know, I'm in a room with a lawyer trying to write a patent. In the end, no patent was filed, and the code was never open sourced. What a waste. Arguably, that was 15+ years ago, it would probably go down differently now...