Jola
Incorrect as far as my research showed. Tribal enemies also give collateral downgrades. There's no such thing as primary downgrades anymore since the fame patch years ago - unless you mean the downgrade you get when you kill a tribe NPC.When you do a TRIBAL fame mission (primary upgrade) you get also get:primary downgrades from their Tribal enemies
collateral upgrades from their Civ friends
collateral downgrades from their Civ enemies
Hence why the article, which is mostly based on my research, doesn't mention anything about primary downgrades - they don't exist as far as I could tell.
Magnitude is a difficult thing to measure seeing as we cannot see the "real amounts" of fame. Apart from the fact that we cannot see decimals, it's clear as day that the difference between 99 and 100 is much more fame than the difference between 0 and 1, so even if we could see decimals we'd have no way to quantify the "amount" of fame that a mission gives.