As someone who recently started a challenge run trying to get definite proof of what does and does not contribute to that counter; you’re correct. Everything that results in either a name or an icon on the map is worth roughly 0.04% each, and things that don’t make names or icons appear are worth zero percent.

• worth one map unit each: locations like forests and bridges, settlements, stables, Forge Constructs and Crystal Refinery (you need to talk to them to make the icon appear), shops (usually auto-unlock when entering a settlement, but each individual icon is still worth the +0.04%), shrines and temples (just discovering them adds to the map, completing them doesn’t increment the counter further), lightroots, solved Korok puzzles (the backpack koroks are worth ONE map unit because it is one single icon, despite giving you 2 seeds), chasms, wells, caves (each entrance is one map unit).

• things that don’t count: quests, memories, sages, bosses, minigames, minibosses, the Hyrule Compendium, key items, special horses, whether or not you spend Korok Seeds, the Master Sword, armor and their upgrades, cooking recipes. All stuff that a sane person would normally include in an “overall game completion” counter.

Funnily, even some “non locations” contribute to the counter, solely because they lead to icons. The Ancient Stone Tablets for example do not yet count if you visit them; you have to take a picture of each and show it to that Zonai researcher in Kakariko, and THEN you get an icon for the ones you have shown him, so the trigger is the picture. Dragon Tears also only count if you actually watched the cutscene, and the shops in Lurelin only count after you helped rebuilding them.