The average temperature sure. But would uneven spots have that much effect on the thermal radiation I get sitting over a meter away?

Less that 2% of insulation being out of place can waste something like 40% or some ridiculous amount of energy. It's quite nuts how even just a little break in insulation can have a significantly negative effect. A few years after I moved into my first home - a townhouse - I added some R-16 bats to the already existing R-12 insulation in the attic and it more than cut my heating bill in half. It was a three story narrow, townhouse - not that much square footage of ceiling compared to the walls/rest of the house but it made ALL the difference. If I didn't live it, I wouldn't have believed it. And I kind of did it on a whim since I didn't need that many and Lowes was having a sale on insulation. I would have done it the first week I moved in and had a couple far more comfortable winters!

Okay but that's not what I was asking. That much heat loss will affect the overall temperature.

He did answer what you asked, but I think you may be losing sight of the forest for the trees here. Maybe re-phrasing will help?

They explained how something could cause uneven spots and low average, as far as I can tell. Because those spots leak so much.

But I want to know if there is a way uneven spots could cause a problem without some effect tanking the average. What do uneven spots themselves do?

The uneven spots may indicate the presence of leaks. The leaks can have an effect on the average temperature.