In other words, perhaps, the coronavirus virus uses long-term infections as a mutational testing ground. While inside one person, they can try out all these different combinations of mutations and figure out, through trial and error, which ones are best at evading the immune system or helping the virus become more infectious.
Nothing new and textbook virus evolution. However, the leap to the last sentence is not and is not the most likely outcome, rather the opposite, in my opinion, and very poorly worded.
And this process is likely happening again right now, worldwide, in other immunocompromised patients. Eventually, these new variants could mutate again and create even more dangerous forms of the virus.