Cogito, it's nothing to do with condemnation or certainty. As more research emerges, we adjust our empirical knowledge and act accordingly. No more no less. Just as we now know the dangers of passive smoking, the benefits of carseats etc. We didn't condemn a generation of children to COPD or cancer or asthma or fatal car accidents, we just learnt how better to minimise risks. And no babies haven't changed much in 12 years. The guidelines haven't either. They've changed from 'between 4 and 6 months' to 'around 6 months but not before 17 weeks'.
The actual guidelines and common sense are quite well aligned imo. If your baby can sit up, pick up food, chew and swallow, they're probably ready for solids. We know this happens around 6 months. Some babies will be ready before, some after. But the guidelines encourage you to look out for these signs in your own baby and to not be led by the red herrings of 'baby watching you eat' or 'needing milk feeds'.
OP, can I tentatively suggest that instead of saying 'I'll wait till 4 months and then try some puree', you shift your thinking to 'I'll wait for the signs and then start'. Because I do believe that of course each baby is different. But what you're doing is deciding to start at 4 months. This is your decision, nothing to do with the actual baby you have as you've no idea what he's going to be like at 4 months. He might have a strong tongue thrust reflex and be unable to sit. In that case it would be likely that his body just isn't quite ready yet.
It's really hard when people around you are probably hung up on numbers ie oh he weighs x amount or feeds x number of times or he's x weeks and still on only milk. It's like the end bit of pregnancy when suddenly you hit this arbitrary due date and people start saying 'haven't you had that baby yet?'. Well all people are different and just as some of us gestate babies for 42 weeks, some babies are ready for solids at 20, 23 or 28 weeks. We can only look at the baby we have. Making arbitrary decisions to introduce solids at x date is the same as whipping a woman in for induction as soon as she hits 40 weeks.
I'd recommend enjoying your baby, feeding him the calories he needs during these periods of massive growth and letting him tell you when he's ready.