https://www.webmd.com/cold-and-flu/cold-guide/common_cold_causes

It's likely that someday you'll have a close encounter with one of these types:

Rhinovirus

Coronavirus

RSV and parainfluenza

There are also a lot of viruses that doctors haven't identified. About 20%-30% of colds in adults are caused by these "unknown" bugs.

Enough that it makes a noticeable number of cases and doesn't render the statement I made incorrect, especially with the mystery 20-30% unknown.