Johnny does these things in the time of the novel in question. That’s how Johnny is, not was.
That's how I'm seeing it. Present tense is looking better to me.
But with describing the novelist's style, I think it's more a matter of distance. Both look fine, but just one of the two might look better depending on the context.
For example, if she's looking back on it and contemplating how this relates to a present situation or basically how it it is able to offer any insight at all into something else entirely, past tense seems to suit this.
Writer’s style was bustling, intoxicating. He always reached something specific but took the long, teasing, route to get there. In SS, for instance, he abruptly broke away from the fast-flowing story to follow a woman who has lost her phone. She led you to a tavern, and to a place that made you question the truths of chapters past. The journey was certainly as important as the destination, but Writer’s books eased their way well beyond this clichéd aphorism.
To me, this looks like a temporary break away from what the narrative's really focused on at that point, and this is going to lend itself to further observation. I don't think this could stand on its own. This is viewed from much further away, as an experience that has already been completed because she wishes to draw from here, what she learned in hindsight and apply it to a current experience or consideration.
Whereas with the one written in present tense, it looks more comfortable in a discussion or inner dialogue. When we're immersed in the book and the book alone, the story/book is not yet in the past. It's an ongoing experience.
I really don't think there's a hard rule for this. Maybe pay attention to how close or far away the characters is from the story at the time that she's thinking or discussing it. And whether it feels as if, depending on the event, she is experiencing its effect currently or looking at it in retrospect.
That's all I can make of it anyway. Hope this helps.