On most cars the fuel light comes on with about 2 gallons left in the tank which will give you 30-50 miles to refuel. The tank on the 2018 Explorer is 18.6 gal which is small when coupled with the 3.5 EcoBoost.
I also have a 2018 Platinum and the small fuel tank is an issue with me. My company vehicle is a Transit 250 with the 3.5 and that was the main selling point for me to buy the Explorer. (On the Transit fuel tank is 25 gal, down from the Econoline which was 32 gal.)
And the fuel keeping the in-tank fuel pump cool is a wives tale. The low fuel light is nothing more than a courtesy. If there was an issue with in-tank fuel pumps and heat the manufacture would put a requirement in the owners manual or just not put them in there.
For more information about battery for coolant for ford explorer visit the website here
https://greencountryoffroad.com/chemicals-fluids/coolant-for-ford-explorer