"Really? Thanks! What kind of pointers? What are we going to practice?" The last thing he remembers from Konoha, Chouji really wanted to play ninja with the other kids. Now he has someone offering to help train him as a ninja. Someone who isn't a clan member or a teacher. It isn't Lee's job to teach him, he's offering on his own. That's every bit as good as playing ninja. maybe better.

Probably best not to practice any of those things in the hallway of the apartment building, though.