It does say 'In silicon valley'. But even after price adjust, that does seem WAY too high for a junior developer.
In general, a publicly traded company is not going to give that kind of package to an undergrad. Maybe $110-120k in salary, but the stock amount is more likely to be around $80k vesting over 4 years.
Would be alot different than 100k "signing bonus", more sane tho.
I'd say $100k salary is very typical, as are the RSUs (vesting over 4 years as you said).
Even non-CS majors. If they studied a quantitative field, can code, and cleared the dev interview, they got that offer.
You have to stay a full year at the company otherwise you have to pay it back. But yes, it is all upfront; cash.
Attending an Ivy makes it easier for you to be recruited, since offers literally find you. At a lesser school you can still do well, it's just you have to find the offers.