I did some more research. "él" can mean "it" at the end of a sentence (see the comment below by alezzzix about unstressed words at the end of sentences). Here's an example from SpanishDict.com: "Cinco a favor de mi plan, y tres contra él." (Five in favor of my plan, and three against it.).
Another opinion: Google translate prefers "No recuerdo mucho al respecto," when the English sentence ends with "it".
A comment by someone knowledgeable would be welcomed.
Lo and le are object pronouns, just like any other object pronoun, they are unstressed, you cannot finish a sentence with an unstressed word in Spanish, hence the rule "don't finish a sentence with a preposition", since 99% of prepositions are unstressed. There are prepositional pronouns in Spanish, and as the name suggests, they are used after prepositions, most of them are the same as the subject pronouns except for mí, tí and sí (reflexive), the rest (él, ella, nosotros, etc.) remain the same
"No recuerdo mucho sobre él"
was deemed incorrect.
But my answer is exactly the same as the model answer given above, apart from my avoidance of "Yo" at the beginning. And everyone knows that subject pronouns are rarely essential in Spanish. I certainly can't see any reason why the subject pronoun has to be used in the above statement.