I can confirm this. If you cancel before the overnight card processing batch processes, in many instances, you won't even see the DL change. I recently booked something at 11 am Sunday, cancelled it at 2 pm same day via an agent, and never saw a charge for it.

With refunds, after you've waited overnight, I've never waited more than 5 business days for money back on my non-DL Amex. Usually its within 2 business days.

I also booked a United flight once via Expedia on Friday, for a flight 2 days later (Sunday). Expedia allowed cancel until Monday evening at 11:59 PM, but I didn't want to push it with United, nor hold a seat that someone else could use. I cancelled it Sunday morning (flight was at 6 p.m. that day) via EXP's websiteand received their refund that same week.