That illustrates exactly the point, though.
Normally when you rent a room for $10, it implies that the room is worth at least $10 to the tenant, and the opportunity cost to the landlord was < $10, otherwise the transaction wouldn't have happened. And similarly, if someone invests $10 for 10% of a company at $100 pre, they're assuming that the discounted cash flows of the company are worth at least $100. People who analyze financial statements and trade in markets assume this to be true - it's fundamental to the price discovery mechanism.
But if the actual cost to the tenant was $0, the value of the service might have been any number greater than $0. And similarly, if all the money in the investment comes back to the investor as revenue, the actual cost of their $10 investment wasn't $10, it was $0. You can't make inferences about what they actually value these services and investments at, because the prices were not set by a free competitive market, they were set by companies colluding (or cooperating, depending on framing) for mutual benefit.
We saw the same issue with all the food-delivery startups that were offering 6 free meals - they booked the revenue and used it to justify outlandish valuations, and they booked the promotion as a marketing expense, but the root problem is that consumers wouldn't buy the product at list price, they were only buying it because of the investor-funded promotion. Or with Groupon - it was economically unviable for the businesses that participated, but they wouldn't find that out until after their revenue could be used to justify the next funding round and cash out in an IPO.
Wash-trading is just the limiting case of this, where it's apparent to everyone that the economic value of the transaction is zero because there is no actual product being traded, but a self-dealing transaction is used to set a price that other participants in the market anchor off of.
The tricky part is that sometimes this tactic can be economically viable, and offering discounted or financed products is a way to get consumers to get over the activation energy of trusting a new product, and once they've converted they become regular customers of the normal product offering and go on to spend a lot more. This is the point of a sale, or a rebate, or a promotion, or a financing deal. Which I guess answers my original question about why it's legal here but not for crypto wash-trades: it can sometimes result in true economic value being provided, and it's difficult to prove malice instead of incompetence.
But the caution being offered in this thread is to not take revenue figures or valuations of AI startups or cloud providers at face value, lest you be the one who is incompetent.