I’ve taken this to suggest he has an eclectic rather than encyclopedic body of knowledge. Having a “well rounded education” is different than randomly jumping

I’ve taken this to suggest he has an eclectic rather than encyclopedic body of knowledge. Having a “well rounded education” is different than randomly jumping deeply into various topics. Abstractly, everyone is limited to finite life experiences. Knowing the earth orbits the sun is unlikely to be irrelevant for a detective, but knowing local soils might be. If common knowledge would have cracked a case there would be little need of a great detective, thus the greatest detective might be quite ignorant of many things. Though obviously Holmes might could be having a bit of fun with Watson.