1) I'll try to figure out the catapult issue. I also noticed that it initially targets the second or fourth tower (it would be better to avoid the term "wall" to prevent confusion);
2) The rules were obtained using the Oracle (there aren't that many variations), and the probabilities were taken directly from the source code. Otherwise, I would have had to run a lot of tests (and that's assuming that the probability of gaining skills doesn't alternate, although in reality, it does!).
P. S. I spent a very long time searching the internet for any information about Heroes, collecting it bit by bit. I still have a stack of printed materials at home (back then, I didn't have my own computer). Of course, I would have liked to find everything at once and in one place :) But, alas... And now we have an entire website dedicated to this wonderful game! Thank you for creating this reference guide!
So, having a good understanding of the game mechanics is, of course, great. But, as you yourself understand, tactics and strategies for successful gameplay are much more interesting. I suggest systematizing the known tactics for conducting battles, strategies for developing cities, etc., and adding them to the reference guide. This would be a great gift for all fans of "Heroes I"!
I've been looking for a long time for a monumental artistic work about Heroes I (something like "How I Became a True Warlord of Erathia" by milordvsk)! Can you help me with that?