At Google you start with an initial large grant that vests over 4 years. For example, let's say you get 400k as stock that vests over 4 years and 100k as salary to make math simple.
So you get 200k the first year, and at the end of the year you get another stock grant that vests over 4 years. Let's say you get 80k.
The second year you get 220k (100k salary + 100k stock from initial grant + 20k from first year's grant). Let's say you get the same 80k again.
If this process continues, the fourth year you get 260k, but on the fifth you will get 180k. Typically what happens is that unless you get promoted 2 times in those 4 years, your salary will decrease substantially on your fifth year.
I've simplified things a bit, but that's the general gist of it.
But given this math, everyone will always see a drop after the 4th year. You can kinda level off the drop if you get promoted exactly as your initial grant runs off, but that's mostly coincidence. If you get your promo grant a year sooner or later, you'll get different drops and hikes.
The author trying to connect the 5th year cliff, which is a common issue, to the lack of promotion, seems a bit misleading.
So you get 200k the first year, and at the end of the year you get another stock grant that vests over 4 years. Let's say you get 80k.
The second year you get 220k (100k salary + 100k stock from initial grant + 20k from first year's grant). Let's say you get the same 80k again.
If this process continues, the fourth year you get 260k, but on the fifth you will get 180k. Typically what happens is that unless you get promoted 2 times in those 4 years, your salary will decrease substantially on your fifth year.
I've simplified things a bit, but that's the general gist of it.