Would you say a 32 year old is in the same age group as a 27 year old?

Yes. Being in 30's is still as young and not so much difference than in 20's in my personal view.

Im 26 and I have friends in their mid 30s who I've known since I was in my early twenties, I didnt even think about it or ask what age they are, we just get on well because we have the same hobby (smoking weed)

Context?

It varies massively from person to person.

If you’re asking if 27 and 32 is an objectively large age gap for a friendship or dating I would say no.

If the age group is 27-32, then you are in the same age group. If the age groups are 25-30 and 31-35, then you are not. If the age group is 20-35, then you are. If it's 30-90, then you're not. If it's 5-30, then you're not. If the age group is 0-100, then you are. Hope this helps.

By then, most people have had their asses kicked by the real world a few times.
I do think there is some maturity difference but not much.

The older we get, the less a few years matters. Like 10 and 15 is considerable difference but 40 and 45 - almost none.

Well, no one is middle aged until 40-45.

They are pretty much overlapping groups, late 20s and early 30s are pretty much the same. If you're talking about specific people then it depends on the individuals' experience, lifestyle, etc.

It entirely depends on what you're talking about.

I think so yes

Yeah, sure