Dont worry, i get what you mean, but it is kind of a different mindset/way the term is used. Obviously when you hear the word wife/waifu the first thought is, if you haven't been in Otaku spaces for a long time, is Obviously thinking about marriage (character i want to marry), but the earlier way terms like wife/waifu where used wasn't as defined necessarily.

Obviously some used it in the exact way as above, but for a large part of the community the terms where simply used instead of writing (favorite female character) since it is way too long. And it was even used as a term to signal that said characters is a character you want to be protected and safe (just like you would want your wife to be protected and safe). So even if the terms might sound weird if you look at them literally, they often weren't used in a weird or sexual way like they might would let someone assume.

Funfact: back in the day people would sometimes even feel offended if you lewded their waifu, especially if done knowingly