Discrimination in hiring happens every day. Be it conscious or subconscious. If there isn't a hard, unavoidable quota no one can force anyone to hire people they don't like. The laws may just forbid them from being this forthright.
Never attribute to malice what you can more appropriately attribute to stupidity. The people who coded this may be young and not even on their first divorce yet. To me, that's what this family plan business falls under. To leap from that to organized discrimination of folks being born out of wedlock seems a tad too conspiratorial from my POV.
This may be a fryable fish. Yet I see much bigger fish elsewhere.
What may also hold back development of functional patchwork family plans is legal hot water. Not every split is amicable. The Googles and Microsofts may simply have decided they don't want to be put in a situation where they need to adjudicate between two warring ex partners whose bitterness is overriding their child rearing responsibilities with petty disputes. And building a system where maybe new partners can gain access - even just by mistake - to their spouse's kids accounts also has very bad PR potential when it turns out the step parent is abusive.
Nevertheless you should let them know about your feedback. Patchwork families are quite common and they can probably do more in that area.
You are judging work by somebody who doesn't feel compelled to follow guidelines made by other people with those very same guidelines. Those other people looked much more closely at flags for geographical entities, not movements, to come up with their guidelines. No one is required to follow them or retroactively abide by them. They are a great style guide but not the law.
Every flag serves a purpose. This flag's purpose is to show representation by color and design for everyone in the community. It's was the point to be busy.
Why don't they just stick with the rainbow flag? Because the idea of the rainbow encompassing everyone was made at a time when gay and lesbians came out with pride but many of the letters that abbreviate that community today were still marginalized more harshly, maybe even within homosexual circles. They weren't all suddenly anthropists and free from discriminatory points of view. Development of ideas and communities takes time. And that's why an artist took ideas from many different flags that were created over time and combined them into one. It is eye catchy and instantly recognizable, even at a medium distance still.
I don't find the result aesthetically pleasing either. But I recognize a) that wasn't the point of it and b) I'm not a member of the LGBTQ+ community. If from within that community a movement rises to change the flag into something else, by all means. Other than that my design opinions - and I suspect many other ones in this thread - are largely academic and frankly irrelevant.
Good flag bad flag is not the gospel. Take it as a starting point for new designs but don't scrutinize all existing flags by it.