It goes in one direction only.
Companies can take open-source software and make a proprietary reimplementation. You can't take a proprietary software and make an open source GPL version.
I am absolutely certain that if you tried you would be sued to oblivion. But big company screwing up open source is not even news anymore. In fact I (still) believe that the fact that even though LLMs were trained on tons of GPL and AGPL or even unlicensed software it's considered ok to use LLM code in proprietary projects is example of just that.
From a strictly legal perspective the two are equivalent. The fact that there are structural injustices in the system is true, but that's not a question that any answer to "what should be legal" can fix.