This is a little odd, but it's not totally unheard of. The way Real Time Carrier Shipping works is that we receive the estimated delivery time from FedEx. It may be that FedEx is estimating the delivery time factoring one day for order processing, and so there's not really much we can do here. I suppose the worst case scenario here is that you're under-promising your delivery time to your customer. If customers reach out with a concern about it, I'd recommend explaining that the delivery times factor in 24 hours for order processing, and are simply an estimate.
Let me know what you think!
I do not see any problem with FedEx Delivery times. Have you double checked it? A quick way to check it to directly head onto FedEx calculator which also shows you the rates. However, if you are willing to add some days for making the product, then you can use the Multi Carrier Shipping label app and with tweak this will be possible. Apart from that the usual delivery days are pretty well reflected using the app.