I remember the first Xmas I celebrated on my own: it really meant so much, as instead of worried about the "pagan roots" I could see it was about sharing it with my GF and her son (she let me share her Xmas with them). Really quite a fond memory.
But yes, the "no birthday, etc" thing falls perfectly in line with the general principle of deprecating the individual vs the group, built on assumptions that mere mortal humans are unworthy of praise, but deserving of condemnation. It's FUBARed with a capital F.
It's also consistent with the reason why some Xians get extremely uncomfortable if given a compliment, and always feel the need to deflect the praise to their creator, "to the Glory of God". This leads to social awkwardness, since they've never learned to accept ANY compliment, so even a polite offering becomes a need to get into how all credit goes to their God, etc. That leads to the impression of their being pompous arses, as they will do this for even trivial compliments. It reminds me of the old saying, "Don't be so humble: you're not THAT great".
But yeah, this is one manifestation of a high-control group, and the mind-reaming begins on Day One (and the parents often don't even understand that they're doing it).
Break the cycle, by all means. Don't live a thoughtless life.....