When I look up supuesto in the Merriam-Webster dictionary, it gives the definition when used as an adjective as supposed or alleged. As an infinitive, it gives to suppose/assume first, a second meaning as to imply/suggest and third, to involve/entail. It doesn't show meant as a definition.
DL's own drop down gives the following translations to the combination "lo había supuesto":
• (I/he/She/it/you) had supposed ( it/him)
● (I/he/She/it/you) had meant ( it/him) || Yet this sentence is not accepted. Confusing... Isn't supposed also what is/was intended/expected/meant (to be/happen)?
// From spanishdict.com I found only this one example sentence where supuesto is translated as meant: ~"Sé todo lo que eso ha supuesto para nuestras generaciones."; ~"I know what it has all meant for our generations." ... Does this go under unconfirmed (supposed, alleged) or an hypothesis (assumption)? The latter?
• (I/he/She/it/you) had false ( it/him) || Btw: had false?? Can that be right? Not rather "falsed", "falsified" or something? If even false anything... closest to it would be falso. Maybe only if speaking of something that was assumed/alleged to be true, but later proven to be false (and the "alleged" is still used to describe it, hence "supuesto"); had a false name/degree/..? But no "had false it/him" - no way, right?
"Assumed" was probably added after people tried it but got it marked incorrect and complained. It is virtually the same as "supposed", and sounds a bit more natural to me. "Suponer" is only translated as "to mean" in my dictionaries as something implied- "la mudanza no nos supondrá grandes gastos" "the move won't mean or involve a lot of expense for us" ⇒ "nuestra amistad supone mucho para mí" "our friendship means a great deal to me" ⇒ "el nuevo método supuso una auténtica revolución" "the new method brought about a complete revolution" (collinsdictionary.com