I find no mention of a "General" Learned in "The Learned Family in America." Perhaps it was just a nickname. I know that there are many Learneds in this genealogy that fought in the Civil War. Whether any were of high rank, I can't say offhand. And my Learned relatives never mentioned anything like this, but it's a big family!
I can also tell you that when I say I didn't find this person, it means that they weren't listed in the index, but I know that the index is not necessarily 100 percent complete. But without any other information about this person, it would be difficult (at least very time consuming) to attempt to verify that that person really existed.
If anyone reading this posting has access to one of the earlier Learned genealogies, they might be able to help. Sorry I can't be of more help.