fischl’s mispronunciation is probably related to how she reads a lot but doesn’t hear the specific words in her day-to-day life, leading to her not pronouncing the words correctly!
hoyoverse has actually commissioned an ad specifically related to this
my gf talks in her sleep like. a lot. and today i'm thinking about a few months ago during winter when she was really cold and she tucked her hands and feet under me and said "osmosis 🥰" in her DEAD sleep. like immediately snoring after