For those that are interested, I did some more digging and I believe I found the reason for this.
I did a chat via iMessage with the sales dept and I was told that the band is not in stock through the apple watch studio builder (and I was given several bands that are in stock).
So I dug further and saw that this specific band is a Spring 2020 band, and from what I've seen before, Apple typically discontinues most of the bands when the next season's bands are released. So it's likely the particular band I chose above (surf blue) is discontinued and will never be available as a combination.
So I ended up ordering one with the charcoal sport loop. ?