I think it was a joke

It is a common social custom in my circles to not use one’s phone when visiting the homes of others as a guest, a faux pas on the same order as bringing an uninvited stranger along as your guest in a visit to someone’s home.

Taking non-macro or identifying photos, especially of the residents or other guests, would be quite rude without advance permission.

I grant that many of my friends and associates may be more privacy-oriented than most, but it isn’t just tech/nerds-who-use-Tor.

I think it is an over-reaction problems that stem from the fact there aren't established cell-phone norms yet.

Some people expect immediate replies to their text messages. This is a big problem with current teens, where their parents will demand this from them. But even some adults do this with other adults. Some people adapt to this by learning they need to respond to every message asap or else! Other people are more willing to treat phone messaging as something that is strictly asynchronous. I think most people are between these two extremes and vary on a case by case basis.

There also isn't consistent norms with how much phone use is acceptable in front of other people. Some tolerate nearly none (see the person you responded to). Some tolerate use motivated by the social situation (eg you look up something directly related to a conversation). Some tolerate only responding to VIPs (spouse, children). Some tolerate any kind of use as long as it isn't too much (I perceive this to be the most common, but it is also the vaguest). Some tolerate unlimited use (I've seen entire tables of people together at a restaurant on their phones the entire time).

One aspect that I find... disappointing is that an individual person's position on the first issue may not be compatible with the second issue. I know some people who would both demand only social motivated phone use when with others, but also demand immediate responses to their messages. To me these seem fundamentally incompatible.

There also doesn't seem to be a social custom of replying that you are with others and won't be particularly responsive for a while.