Earlier quoted context omitted.
Better in-house training would allow companies to increase their potential candidate pool.
Sure, most forms of education will increase the candidate pool in the long term. But in the short term there isn't much you can do to increase the candidate pool, you can only shift candidates from one company to another.
In my (admittedly brief) experience at a FAANG I also noticed there were some very menial tasks taking up engineer time. I'm pretty confident there is work to be done at these larger companies that could be satisfactorily accomplished by someone within their first year of training.