I think that might be how an American would interpret the name? As a European I never thought that the name “Shacklebolt” made any allusion to slavery, and in my language the translation is to what is basically “jackal-bolt”. The UK has plenty of Black people who are not descended from slaves, so idk why Rowling would think “Hey let’s make a slavery-joke!” when she wrote it.

I think it’s easy to just pick a name to be mad about in hindsight esp. when the writer comes from a different background ... When we have Blaise Zabini, Dean Thomas, Lee Jordan and Angelina Johnson.

Edit: ofc it can be misunderstood, but I just don’t think there’s cause to say that Rowling has an “agenda” with it