I reckon he means everything as the pihole operates at the DNS level. Thing is whilst it works against a lot of bloat, telemetry etc. I have seen the kids devices (tablets) and wife's phone where some of these things get round it for sure. You also have the issue as some have posted earlier that random things stop working, so whilst I agree it is a must have tool in your setup these days, to naively think 'oh my pihole blocks everything' smugly is ridiculous. All of the top tech companies out there will be finding ways around this stuff, or it will break genuine operation of how some comms work.