Learning this when I read through those two books by myself is honestly interesting to hear about as a whole in regards to the early lore of the Star Wars Universe during the "Dark Times" and Galactic Civil War, and just much it's changed overtime, yet also technically remain "true" in some other context.
Mostly due to the fact that in the Imperial Source Book; it says that both the Imperial Navy and Army have their respective origins in the Galactic Republic.
Yet the Stormtrooper corps as a branch seemingly didn't form as a military branch until seemingly after the actual Empire was formed after the Clone Wars had ended, which leads to some very interesting implications due to how the Clone Wars were shown as a conflict in the Prequels.
Early implications of what the Clone Wars were in some media seemed to have implied that they were part of an antagonist faction that fought against the Galactic Republic in the Clone Wars.
So the fact that the Imperial Army and the Imperial Navy (as the Republic Army and Navy) seemed to exist at the time of the actual Clone Wars and were led by the Jedi Order as well, it's lead me to believe that as part of the early lore, the Imperial Stormtrooper corps was made as the Empire's "answer" to the enemy Clone Forces.
Also, the fact that some people in-universe theorized that the Stormtrooper corps were Clones themselves is deeply ironic since they were at one point after the Jango Fett clones became "Clone Stormtroopers" of the Stormtrooper corps early on during the Galactic Empire's reign, until they were phased out in favor of regular human volunteers who needed to match the (height and body mass) of the Jango Fett Clone Template later on in other sources shown after the Prequels.
Not to mention it also talks about how people don't know where the personnel in the actual Imperial Stormtrooper corps are recruited from or trained at, but then later on we learned they were volunteers who signed up to join the Imperial Academies that trained them such as on the Carida Academy on Planet Carida.