That's not exactly true. Referrer is only hidden if it's explicitly asked by using a meta tag:
<meta name="referrer" content="no-referrer" />
Or by using Referrer-Policy:
Referrer-Policy: no-referrer
The default behavior is no-referrer-when-downgrade. This means that referrers from https to http are hidden. But https > https is still visible. And with https adaption reaching saturation, referer headers are usually still sent.
