I'm not denying you're experiencing this, I believe this issue occurs for you and likely has occured across OS and/or application versions.

My personal MacBook had 8GB of free storage (4.2GB after my test recording). I experience issues with programs like xcode failing to compile or crashes when I open too many files, pages hasn't been able to save a file since the machine had 15GB+ free.

I just download, installed, and recorded 10 minutes of desktop footage with a webcam overlay and audio. Nothing unexpected happened. I watched all 9 minutes and 28 seconds of it and it looks and sounds exactly as I would expect.

I spent my time doing this and writing this comment not to belittle you or your experience, though at this point I would ask you what do you expect to happen?

You did not post an existing bug report, or write one yourself. You've provided no evidence that anyone who contributes meaningfully to the project has experienced or even heard about this issue, let alone anyone who operates the project or consumes it from macos has any notion it is an issue.

Again, I believe this is a real issue. But there is no information here to go off of, especially with my experience, that points to anyway to meaningfully improve an OSS project in regards to your experience. If nobody with the requisite experience is asking the right questions, this will not get fixed. It starts with those people having any information to start with.