That's completely different to doing a week of enterprise support for a large company on a product with millions of users.
One is more like helping a product find its product-market fit, validating ideas, or even realising the company needs to pivot.
The other is mindless, boring and in 99.99% of cases unproductive for the product.
In startups there's a push for founder-led sales because it's the best way to learn from your target customers.
It's the same for engineers. The quickest way to validate your assumptions, see where the rough edges are, identify an easy bug, etc. is directly from the customer.
I found that doing it myself with a support rotation was the best way to do this. That said, it's not "throw engineers into the deep end". It was managed by support team to optimize my time and their benefit. We were able to mutually teach each other a ton.
I've done tons of direct customer support over my career. I still do sometimes, and I lead my department. (No, this is not a waste, it has a strategic use of my time to keep people happy.)
The message I'm responding to doesn't point in this direction, but so many other comments make it clear it is a status thing for them, that they consider themselves above directly serving customers.
All I can say to those people is don't leave your cushy HugeCo job for a real startup. You will have to humble yourself in far worse ways than asking, "how can I help you?"