According to Wikipedia the system has significant buffer capacity:

> Fifteen associated tank farms... provide a 45-day supply for local communities.

Such buffer capacity makes sense considering how long deliveries actually take:

> It generally takes from 14 to 24 days for a batch to get from Houston, Texas to the New York harbor, with 18.5 days the average time.

See https://en.wikipedia.org/wiki/Colonial_Pipeline

Also consider where the shortages are occurring: in sprawling, rural and exurban areas where the last-mile infrastructure is likely exceptionally thin; that is, much less able to handle surges. It's not just computer and car manufacturers that optimize for "on-demand inventory"--i.e. cut carry costs to the bone, sacrificing volatility resilience.