Just on the iron point, a full term baby whose cord was not clamped until it stopped pulsating has more than enough iron stores to last it until 9 months at the very earliest, so there is absolutely no need to worry about shovelling in 3 meals a day at 6 months on the dot to get iron into them. The nutrients babies are most likely to need from solids first (and again, not 6 months on the dot) are zinc and iron, so it makes sense to introduce some foods when starting solids that contain these minerals. They only need tiny additional amounts of them and can easily get them from gumming a piece of turkey or beef.
If a baby is gagging an awful lot, it means they have not yet lost that protective reflex and aren't actually ready for solids yet. they all develop at different rates, but these reflexes are unlikely to have gone by 5 months. See here for signs of readiness.
Even babies right at the top of the centile chart can continue to thrive on breastmilk if fed whenever they ask for it. I know lots of them
.
As for how much they eat, well my eldest was shovelling in 3 meals a day with his hands by 7 months. He could eat wheatabix or porridge, most of a banana, risotto, breadsticks etc, shepherds pie
. He just wolfed down whatever was put in front of him and continued to breastfeed loads round the clock too. He was obviously very hungry because he ate. He was on the 0.4 centile. DC2 was a bit slower, more like 1-2 meals a day at 9 months. Just wasn't as interested. Dc3 (my biggest baby) was happy just to stay on breastmilk as long as possible and showed little interest in more than tiny mouthfuls of food until after her birthday.
Tbh I'm not sure what point you are making. Why do you feel the need to criticise what other parents are doing? Giving finger foods from 6 months is recommended and pureeing is unecessary, as all babies, even if spoonfed, should be able to cope with food mashed with a fork from 6 months (the recommended age for introducing solids). Allowing them to explore food and different texturtes with their hands is considered a good thing developmentally, so it's not much of a leap to just let them feed themselves if they want to.