Well he's 4.5 months now (a week and a half to 5) and I've been occasionally testing him. For Easter dinner I put two little soft pieces of green bean in front of him and he had fun... smashing them with his rattle. No effort to pick them up or sign that he even knew they were food. He was hungry at the time because he asked to nurse halfway through dinner and I fed him but his opinion on the green smooshable stuff didn't change.
He does sit a little while on his own now. Its hunched over and leaning forward but he's making progress.
If he's not interested, why not just wait? I just don't understand the hurry.