It seems like this could be explained by something as banal as sinus congestion causing/worsening COPD. And the link between gut health and general sinus congestion seems natural to me.<p>Articles like this tend to paint gut health effects in some kind of supernatural light.
My dad had COPD later in life, and I can attest that he was not a person willing to eat much fiber; I could easily believe his gut microbiome was screwed up.