Not sure about this. It is fine to have lunch together twice a week. Do it every day? Unless someone really enjoys talking and being listened.
I enjoy discussion with colleagues. I find, though, if more than 4 persons are involved, it is more efficient to be in a formal place or follow a formal procedure. Otherwise, 90% of time tends to be on trivial issues.
If lunch together is for socializing, I don't see why twice a week is not enough. I worked in such an environment before and the topics during lunch were mostly the same everyday. Most topics were not interesting. To be fair, it is hard to have an interesting or insightful talk with 10 people. The talks that made me think and made me intrigued were always with 1 or 2 colleagues. We can go out for a drink. If the topic is work-related, we can have a 15 minutes coffee break and discuss it.
I understand that lunch is also supposed to give people a break after working hard for 3~4 hours. But lunch together might not be a break for some people. Sometimes after constantly working for 3 hours, especially if the work requires me to be very concentrated, I just want to have a quiet lunch time, to relax, to read 20 minutes of history or other books to adjust my brain, to plan what to do in the afternoon, or walk in the sun for 10 minutes. At these occasions, lunch together and talking to other people only make me exhausted.
People are different. It is fine, though, if the boss wants to establish this lunch-together culture and exercise the cookie-cutter. There are always start-ups that don't require this.