Gear inch/ratio question

Man rides bikes but doesn't understand gears. This man right here say whut?

Why would riding fixed be any different to riding singlespeed while going uphill? Both are exactly the same while you pedal forward. only difference being is that you can stop pedaling with one.

I suppose because riding fixed is a completely different experience in every other way.
Why not uphill as well. The bike is great, yet going up the same hill with the freewheeler
is easy, the fixie seems to stiffen up when climbing.