I think it's effectively closer to 2X than 4X. When I started as a new grad, I also had some RSUs and a sign on bonus. My employer didn't go public then, so my RSUs were not liquid, but I'd say my compensation was effectively $225k first year even though I couldn't cash out most of it. It's a different story now that my employer is public

My first promo put me in the $275k-ish range, and my second promo put it in the $350k-ish range. My base salary is $220k now, and the remaining $230k is stock and bonuses. IME, getting the first promo is not too difficult, but I had to put in a substantial effort for my second one, and hit some rough patches along the way. Any promos after that are a bit of a crapshoot, and more political than anything. The politics favored me in this case.

This tends to be the usual career trajectory at Facebook or Google, or some of the smaller public companies (Uber, Lyft, Square, etc.). It can be more volatile at smaller companies, given that stock based compensation is a significant portion of your total compensation, and you're taking on more risk.

I stayed more or less in the same engineering role throughout my career. I think skyrocketing senior engineer compensation is a relatively recent (i.e. ~4 years ago) trend, while new grad salaries were pretty high even 10 years ago.