It's not about weight or incline, it's the mechanical gearing in the "transmission" that can't turn the wheels without 100 percent power from the engine. You'll be able to push it and think it's really heavy, but it's just the transmission fighting you.

standards and automatic trans have neutral that disconnects driveshaft from engine, removing any resistance from the engaged gear. Most EVs either don't have neutral or a poor implementation of it, because of single gear transmission/direct drive.