I Highly recommend customizing your harness a bit to fit your needs!
I have everything paracorded to mine, my gps is my most valuable piece of equipment. it's got it's paracorded loop on my non buttstock shoulder. My phone case is on my shooting side but low enough to be out of the way. My buck grunt and doe bleat and a canister with milkweed are paracorded and put in a pocket. I keep the lanyard on one side in its pocket and my lineman's belt on the other. I have a holster for my pistol and a pouch for my range finder.
Everything is secured and has a specific spot. I literally can run through a briar patch in the dark upside down, falling and crawling and can't lose anything. I've lost stuff in the past. I've had to go with my gps and retrace my steps sometimes for miles. It's not fun and losing stuff gets expensive.
Adding a phone pouch to my harness is the easiest and best decision I've ever made. If I fall there's a very good chance my phone will be securely in its pouch.
If you fall and can't get back up, and your phone is in your lap, it's not gonna do you any good laying in the leaves while you dangle.
My phone has fallen out of chest pockets and getting a phone in and out of pants pockets with a harness on is a real chore. A phone in your pants pocket also tends to chaff on long walks.
I wear hip boots and wade through a lot of water. I have been soaked from waist down before after a fall or mishap. I like having my phone higher on my body so it has a better chance of staying dry.
Wear a harness and customize it to work for you! adding a phone pouch is a cheap solution that could keep your phone from sliding off your lap and banging off your stand when that big buck comes through!