Companies that really hire the top 5% of candidates, never advertise open positions. At most, their careers page says that they accept applications at any time if you think that you fill the bill.
Most of their hires will come from reaching out to people and referrals.
top 5% is a very relative description. There is no hard measure, and everyone have a different standard on what they are "measuring in their head". Our perceptions are extremely biased by our own experiences. 90% of the time I really have to get to know the candidate before making any decisions. Of course the biggest constraint is available qualified candidates at the time. That's why hiring is so hard, and people who are really good at it tend to be veterans who have been in the industry for a long time.
Most of their hires will come from reaching out to people and referrals.