I'm not sure why there is so much anti-Mozilla hate. I know they're far from perfect but they do an awful lot for the open source world. Having an open database for voice training seems like something that the world can use to do some good.

Because the genetics that build the vocal tract could be different, which in simple terms could mean a change in pitch. There are also more cultural differences such as speech cadence, accent, and inflection.

Technically there are different dialects and a lot of unique slang, idioms and specific descriptive words.

In the trans and non-binary community for instance there's a lot of terms regarding how people identify and express themselves that unless you know the actual function of how they work aren't easily indistinguishable from slurs to outsiders. Take "Femboy" and (please forgive me mods) "Shemale". The former is a perfectly socially acceptable description of a guy (cis or otherwise) whose gender expression is very feminine...the latter is a slur that places emphasis on the birth sex characteristics of a trans woman and implies heavily they are guys just pretending to be women and the term originates from the porn industry that fetishizes trans women.

You also have the usage of neo-pronouns. In languages with more gendered components than English sometimes what words are chosen either reflects the gender of the speaker or the person being addressed or objects can be given a gendered connotation. Some languages are actually very gendered and the usage non-binary folk using those languages make whole new conventions. English speakers whine a remarkable amount over they/them singular pronouns are confusing but ain't seen nothing. A lot of places your job title and status has no neutral gendered term or culturally there are sentence structures that differ down entirely binary gender lines. Are you latino or latina? Guess we need a new word... Latinx!

Have you seen how (even if stereotypical) black folks talk vs white folks (in media)?
Just turn on GTA 5 and listen a bit to Lamar and Franklin talking in missions.
So much slang is in there.

Right? Like we all are made the same on the inside

Dude, I clicked on the link pretty excited to volunteer. I have a professional mic, a little time, and a decent voice. The first thing that greets me is “Voice datasets also underrepresent: non-English speakers, people of colour, disabled people, women and LGBTQIA+ people.”

Well, I’m none of those. So maybe they don’t want my donation, or I’d spend time and they wouldn’t use my recordings... Sort of a letdown.