But that's implying that only mothers give birth, and erases those who don't identify as mothers who give birth.

That's how I understand their thinking, at least.

I agree with you and think anyone who is offended by motherboard is silly. I'm sure it was never even anyone that was actually offended, but a group of people sitting down and looking at any and every word that has any type of gender connotation and saying that's a bad thing.