I suspect Larian is using levels for all the RPG gamers out there who need to know how awesome they are for having beating a level X creature. The creature levels do not match with their D&D CR, so it's pointless information, even more when they buffed certain creatures anyway.
For example, Haslin is not a level 5 druid. He can cast spells while transformed into a bear, that means he is at least level 18th. His HP match a level 18 druid too. You can take have him as a temporary companion to clear the goblins. I suspect many people would complaining if he read Level 18 or CR 18 instead of just level 5.
