Technically they could also also be functional teams with a long history of gradual point drift... Though most organizations shake teams up before then.

If a ding that gets mentioned in planning is 1 point and they regularly try to fit 144 point projects in a sprint without splitting it up, that's likely to be rather dysfunctional.

I mean it is possible that gradual point drift would get there. But sufficiently improbable that I know what I'm betting on.

For some reason we are using 20 instead of 21. I didn't even bother asking why

That is because fibonacci is used to indicate the ‘guess’timation part. 5 Instead of ‘twice as much work as a 2’ (4). The idea is when you get higher numbers the opposite happens: 21 sounds like a very specific number and not like a rough guess. 20 does.

So it becomes 1 2 3 5 8 13 20 40 inf ?

By that logic shouldn’t people just do 1 2 3 5 10 15 20?