I have submitted my app before and it was rejected. When I submitted it, it was reviewed within a day and rejected that same day. I have submitted it now and it still says "in review". Tt has been 24 hours. Previously it has taken 4 hours.
Until recently (like the last week or so), App Review would take 4-7 days. This was for full reviews, updates, rejects, etc. Somewhere within that 4-7 days you'd know if it was accepted or rejected.
You're experience with App Review is now the new normal. For example, I have an app that has been 'in review' for 24 hours and I'm not concerned at all. I'm used to waiting a week or so to find out if I've been approved or not. I wouldn't worry if I were you.