"Finger wave it away, it's fine, it's isekai after all." Author probably lol
Yeah, it sure sounds like it. While historical material does contain information on strategy, you won't learn to be a competent commander just by studying it. That's because the most you can really get out of it is that you should try to catch the enemy force at a disadvantage or manouver so that you face smaller parts of it, defeating them in detail. It's not that much help in learning how to accomplish that in specific situations. Much more so here, where magic exists and the MC has no real idea what is possible and what not.
On a side note, it would be supremely funny if it turned out that the MC's "knowledge" consists mostly of quotes from wise figures like Sun Zi. I'd also throw in some Bruce Lee and Yoda! Sadly, I think the author takes himself far too seriously for that.