But, the point is, code and patents aren't one in the same, and submitting code doesn't imply anything about patent ownership or rights.

For example, I could try to submit a pull request to an audio/video project to add an H.264 decoder/encoder that I wrote myself. That is OK because I wrote the code, and therefor I own the copyright to that code.

However, anyone who tries to use this code can be sued by MPEG LA for money or they can even ask them to cease and desist outright if they wish -- because it's their patented technology! It also works the other way around, if I wrote both the code and acquired a patent for the technology.

A CLA is the only way to stay safe, as far as I understand, but most open source projects just don't use them (except very large ones, like the Linux kernel etc).