In many of these words you mentioned, it doesn’t mean “by means of.” It means “from” or “since.”
以前 “from before then”
以後 “from after then”
以上 “from there and up”
以下 “from there and down”
An example of it having the “by means of” meaning in a compound is the reasonably advanced word 以心伝心, which means when two people seem to communicate without words. “by means of heart, communicate to heart”
So… I think this is just a failure of the English resources that use “by means of” as the primary meaning of the kanji.
If you want a source for what I said, check out the meaning section of its entry on Kanjipedia
Probably one of the contributing factors to choosing “by means of” as a primary meaning for it, is that the word 以て (もって) is written with this kanji, and it means “by means of.”
So people probably think “well, when you see it alone, this is what it means” and go with that. But 以て is usually written in hiragana, and it’s an N1 level word, and WK doesn’t even bother to teach it.