I think the argument is that the valuation is so high because the enormous growth IS priced in, but still being far from guaranteed. Meaning there's only downside: if the enormous growth is realized it would be a wash for your investment since it is already priced in, and in the plausible scenario it fails spectacularly or only grows moderately your investment will lose a lot of value.
It's an IPO, nothing is "priced in" until is actually being transacted in the secondary market
There's a good reason IPOs are shown to underperform the market
Yes, lots of downsides on this one, but people see it as a call option on a future where AI replaces all jobs, what would you pay for that? A rational response from someone that accepts the premise of the question is likely "anything"