Huh. This is a rare column from you that I disagree with almost entirely. I guess to start with what I think you get right, there's no need to apologize for being out of office, and no one should feel obligated to deal with anything other than a legitimate emergency (which are, in most fields, truly rare) while on vacation or while taking time off.
When customers receive automated messages, they have expectations about the wait duration (in terms of number for e.g. 4 mins or 4th position), that can make or break their customer service experience.

I might sound nitpicky but the language is important. “Might” or “may be” or “slower than usual” are vague and don’t offer the sender all that much information about when you’re really going to respond to them. Worse, they do a horrible job of protecting the time of the email receiver who, as the responder notes, is not in the office! Such a responder implies that, not only will the vacationer reply to the email, but they may not even miss a beat. They may be slow to respond, but they also might not.
Pro tip: The first works well for both voicemail greetings and email responders, while the next two are most appropriate for emails.