There’s a script that lets you modify the questions, and you can use that to add cues that force you to ignore the synonyms:
So for the question “truth, fact, reality” – you can add “(not: 本当、実)” to the question.
or, if you didn’t want to give away the 実 character, add "(two kanji, not 本当)
Or even better, add more to the question that gives the nuance of the definition of that particular word.
I’ve used this technique in Anki and Skritter as well and it’s solved the synonym problem for me. It’s a little extra work to add them in, but the act of doing it helps solidify a bit, so it’s not a waste of time. It’s a little better than adding answer synonyms, because it forces you to learn all the words rather than one correct answer that works for several questions.
note: the stuff you add using this script only works locally on that one device, which is annoying but better than nothing.