I understood it as, OpenAI is giving AMD money, by buying 6GW of GPUs from them.
But if it results in their stock reaching 600$, then AMD will give back the money that OpenAI spent on GPUs as 10% stock options into AMD.
Which sounds like, no one is really investing in each other, they're both like exchanging money back and forth, where both hope to gain some extra money by propping up the AMD stock with the announcement, hoping it helps make AMD more competitive on the GPU landscape.
