One time a few years back, I was serving as a temporary worker at Brooklyn Bethel. At lunch, I personally observed Sister Suiter (Grant Suiter's widow) exchange a "joke" birthday card with another sister. I kidded with them about it and I could tell it made them uncomfortable that I had seen them and they didn't know who I was or who I might tell. LOL
As an elder, I received a couple "joke" birthday cards from other elders. My witness grandma used to call everyone in the family on their respective birthdays just to remind us of the day whe first met us.
An elder in a congregation had an adopted child and they used to celebrate the day they adopted him. I used to joke with my wife that maybe JW's could celebrate "day we brought you home from the hospital" day with our kids. It wouldn't be a birthday, but it would mock the restriction.
There is a very casual view of the restriction on Birthday celebration among JW's