As soon as he wakes up I change him and feed him and put him back to sleep. I don't feed him 12 on the dot but he normally wakes up around those sort of times 12, 4 and 8, it's just recently he's sleeping a bit longer. But the minute he wakes up I make his bottle and feed him
You are feeding on demand them. You're just following baby's lead and that's great.
Baby has clearly just fallen into routine naturally. Some do, it's not a problem.
In terms of your original question, if baby wakes and is fed at 9.30am, I would feed again at 12pm (as per normal routine) if baby was awake at that time, then follow as you normally do.
If baby is asleep, just feed when waking and go from there.
It might be better for you and baby to start regulating "morning time", so set an alarm and get baby up at a regular time, if not already awake. Say 7am. That regulates the 7am feed, which sets up the rest of the day.
The problem many posters on this thread have is that it's rare to have babies this uncomplicated and simple so young. It will be especially alien to breastfeeding parents. But there is nothing wrong with what you are doing, as long as you never leave baby hungry.
I had a baby born routined. A single 1am night feed and 4 hourly daytime feeds from literally Day 1. By 7 weeks old he was feeding 3 hourly (almost exactly) daytime and sleeping solidly 12h at night.
I have 3 other children (younger and older) nowhere near as easy as DC3. But such children are not unusual or uncommon.
they don't half make some parents angry at the idea and convinced you're lying though