I don't think Achilles would send out a young adult out there without the proper training.
Oh I'm sure Connor was trained well enough, but I guarantee He could have come away with more knowledge, plus I'm sure his short training period didn't help with this either. --- It took hundreds to kill me, but I killed humans by the THOUSANDS!!! Look at me!!! I am sublime!! I am the TRUE face of evil!!!
Someone as old and presumably experienced as Achilles could have continued to imbue Connor with knowledge long after the physical training was done. I think there has to be some form of cut off point where one decides to just let Connor go on his own and learn things on his own rather than passing down everything Achilles knew. Narration made it clear that he trained Connor in both physically and mentally; if there was anything that indicated that Connor was lacking knowledge, I think that falls on his own incompetence rather than being poorly trained. --- "Cat.The other white meat."