Domestic violence is a broad category that includes everything from elder abuse to child abuse to intimate partner abuse.  Your mistake is thinking that domestic violence is the same thing as sexual assault by intimate partners, the latter being only a small subset of the former.  

If it's true that LGBTQ people have higher incidence of lifetime domestic violence, that could be because they're more likely to be bullied by their siblings as kids for all you know.  The point is, we can't know from the stat you posted..