16 And the Lord God commanded the man, saying, “You may surely eat of every tree of the garden, 17 but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall surely die” (Gen 2:16-17).
i) Some readers puzzle over the timeframe. After all, they didn't expire on the day they ate the forbidden fruit. However, I think the explanation is that "on the day" is idiomatic for "when." We have the same idiom in 2:4.
ii) However, that's not my main point. Most young-earth creationists deny animal mortality before the Fall. Jay Wile is a notable exception.
iii) If, however, there was no human death or even animal death before the fall, then Adam (and Eve) had no frame of reference to understand the penalty.
If there was animal death before the fall, then that would at least be analogous. But according to most young-earth creationists, there was no death whatsoever.
In that event, what did the penalty mean to Adam and Eve? What could it mean? They had no experience with death of any kind. No standard of comparison.
The best one could do is postulate innate knowledge. That, however, is not an exegetical argument.