Also not true. In the places I've worked, christmas/easter/summer parties or whatever for specific groups focused on diversity were pretty normal. Not least because often these groups didn't feel comfortable at the "traditional" Christmas party.
I had a client once who asked me to help them with some of their internal comms and staff stuff. They had lots of money to throw at the problem and were very generous - lots of drinks out, wine tastings etc. their big issue was that as mid sized firm, they were struggling to get the front office fee earners and the middle/back office teams to be aligned/get to know each other.
When I asked about the religious, ethnic, gender and age make up of the respective teams, I wasn't shocked to hear that the front office was mostly men, mostly white and with a leaning towards either very young or the very senior, established older (partner level) people. The middle/back office was much more diverse - people of colour, a small but strong group of muslim employees, women etc. Also, all being paid significantly less.
On my suggestion, they'd did some internal research and I was not shocked to discover that the middle/back office people were not attending the laid-on events because they didn't want to drink, they had caring responsibilities at home, they were being paid less and frankly didn't want to do out of hours activities for no extra pay etc etc etc. The event they were laying on to boost team morale, build relationships etc were NOT effective or appropriate.
Last I heard, they'd initiated a monthly Friday lunch, mandated that at least half the partnership attend and were looking at a variety of additional options.