Your reference is exactly what I'm getting at.
The "have done" thing functions to describe how past actions effect the right-now moment. Right the point you're talking about it. That's why the textbook says "have seen it yesterday" doesn't make sense. Every have-done virtually implies rather "have done (by now)" than "have done yesterday".
Let's go to the movies, I heard "On Stranger Tides" is good.
Sorry. But I've just seen it (just now, by now, by the time you are asking me to see it right now).
I thought you watched it yesterday.
I had seen it the day before yesterday. (Here is how "had seen" has to be used. ie I had seen it BY sometime in the past, rather than "by now" as in "have seen it (by now)". )
When it's not very necessary to emphasize "how past actions effect the current situation", like your initial example, you won't have to use "have-done", so "saw" works here, too.