From what I understand, even larger connections fail with aluminum. But larger connections tend to be more professionally done and there are fewer of them statistically. There are many connections in a house branch circuit. Only one has to fail.
This house was built in 66 and there are no "purple" connectors that I can see. Plus, the house is on a slab with cathedral ceilings between two areas of the house so I don't know how they ran the wire. From my reading this afternoon, you are ok with 12 awg in most area's of the house but must have 10 awg in the bathrooms, kitchens, and such area's. I observed only a 14 size within the 2 outlets I pulled.