I don't really understand how it is round tripping.

In the end, Nvidia will have OpenAI shares, which are valuable, and OpenAI will have GPUs, which are also valuable. It is not fake revenue, the GPUs will be made, sold at market price, and used, they are not intended to be bought back and sold to another customer. And hopefully, these GPUs will be put to good use by OpenAI so that they can make a profit, which will give Nvidia some return on investment.

It doesn't look so different from a car loan, where the dealer lends you the money so that you can buy their car.

A dollar is always a dollar, so it's hard to claim that $1 million in revenue is actually worth $10 million. OpenAI shares, on the other hand, aren't publicly traded, so it's much easier to claim they're worth $10 million when noone would actually be willing to buy for more than $1 million.

It's not necessarily manipulative but it's also not exactly an arms-length purchase of GPUs on the open market.

It looks like NVDIA looking to move up the value chain to have a stake in the even higher margin/addressable market instead of simply selling the tools.

If OpenAI doesn't pan out than Nvidia has worthless OpenAI stock and OpenAI has a pile of mostly useless GPUs.