Leashes are for animals, as a way for a human to exert control on them. Putting any person on a leash would seem to me to be pretty demeaning. The symbolism is pretty plain there, and I'm dubious about claims that the author didn't see this.
In part, this is what sensitivity readers are, for specific topics. And, even normal editors fill this role to a great degree.
Beyond that, though, there's no assurance about interpretation. Authors and artists should generally be aware that in any work, there are at least three things: What the artist intended, what they actually did, and what the audience got out of it. While the artist wants these things to be similar, you don't get to control the world.
No. Art is an attempt to communicate. If you are not considering your audience, thinking about who you are trying to communicate your ideas to and what they are going to think, you're going to do a poor job of communicating. If you need help to think about your audience, then you ought to get it.
So, there's a major point you seem to be forgetting - absolute tons of stuff is getting published all the time. The, "twitter mob," as it has been called, has not seemed to be a real block to things getting written and published.
Either, you are being a bit paranoid, and such steps aren't usually needed, or they are needed, and for the most part common editing and the occasional engagement of readers to help smooth rough spots is doing the job without much issue.