I have to chime in and say this feels a bit underthought feature. I use a throwaway email for everything possible, and I would imagine a large portion of Fediverse users do that too.
I also get the motivation behind the feature. I didn't feel like throwaway addresses are worth it before I started using them. They may seem like an obvious spammer flag. But I'd say it's 50/50, just like with any free email provider like gmail or Proton mail.