any more than "sorting pebbles into prime heaps" means "doing whatever pebblesorters care about"
How specifically are these two things different? I can imagine some differences, but I am not sure which one did you mean.
For example, if you meant that sorting pebbles is what they do, but it's not their terminal value and certainly not their only value (just like humans build houses, but building houses is not our terminal value), in that case you fight the hypothetical.
If you meant that in a different universe pebblesorter-equivalents would evolve differently and wouldn't care about sorting pebbles into prime heaps, then the pebblesorter-equivalents wouldn't be pebblesorters. Analogically, there could be some human-equivalents in a paraller universe with inhuman values; but they wouldn't be humans.
Or perhaps you meant the difference between extrapolated values and "what now feels like a reasonable heuristics". Or...
What I meant is that "prime heaps" are not about pebblesorters. There are exactly zero pebblesorters in the definitions of "prime", "pebble" and "heap".
If I told you to sort pebbles into prime heaps, the first thing you'd do is calculate some prime numbers. If I told you to do whatever pebblesorters care about, the first thing you'd do is find one and interrogate it to find out what they valued.
There seems to be a widespread impression that the metaethics sequence was not very successful as an explanation of Eliezer Yudkowsky's views. It even says so on the wiki. And frankly, I'm puzzled by this... hence the "apparently" in this post's title. When I read the metaethics sequence, it seemed to make perfect sense to me. I can think of a couple things that may have made me different from the average OB/LW reader in this regard: