It’s a no true Scotsman scenario. Obviously working on a “startup” in a big company isn’t the same as starting a new company.

But... you get to enjoy the bigco benefits and security while avoiding a lot of bigco bullshit. I did something like this in a public sector org. We got to do something new and exciting, many of the team ended up getting promoted, and the big shots got to pay themselves on the back too. We did not get rich, but we did not risk much.

Generally speaking, if you want to build wealth on a short horizon, working for someone is the hardest path.