Hard bounces are permanent. The address does not exist, or the domain is wrong. The receiving server rejects the message outright and will keep doing so. These are the ones that damage your sender reputation, and these are what Scrubby is built to catch.
Soft bounces are temporary. The message reached a real address but could not be delivered right now — the server was offline, the mailbox was full, or a spam filter did not like your sender score, domain reputation or content.
Scrubby catches hard bounces, not soft ones, and that distinction is worth being clear about. A soft bounce is not a property of the email address; it is a property of your sending setup and your content at that moment. No validation tool can tell you in advance that a specific mail server will be down next Tuesday, or that a filter will object to your subject line.
What you can control is that every address on your list is real. Get hard bounces under control and soft bounces become a deliverability and content problem to tune separately.