That sounds problematic. Where do they detail this?
Wikipedia:
Google Safe Browsing “conducts client-side checks. If a website looks suspicious, it sends a subset of likely phishing and social engineering terms found on the page to Google to obtain additional information available from Google’s servers on whether the website should be considered malicious”.
You want Matrix. Synapse if you intend to host for others, Conduit if you just want to host for yourself. There are quite a few different clients but I do indeed use ElementX on mobile.