Ah gotcha. Too bad it doesn't fit horizontally. What about the front open pocket? Same thing as back pocket?
Sorry, late reply! So I saw these at Dillard's again yesterday and stand corrected. My phone does fit horizontally in the back pocket. I have a iPhone 7 (not plus) with a basic Kate Spade case.
I think when I tried it last time the saddle bag was stuffed with so much stuffing that the pocket was tight. The one yesterday had minimal stuffing so it slid in horizontally just fine. I also tried the under flap slip pocket and it fits horizontally in there too, a little easier than the back slip pocket.