Genetic drift that fixates 14 new mutations, including deletions, in the most negative selected gene in this virus is an abomination, almost statistically impossible, very very close to 0. Even if the incubation and infection time inside this one individual was enough for 1,000,000 generations there's no way for something like that to happen.
"The accrual of 14 lineage-specific amino acid replacements prior to its detection is, to date, unprecedented in the global virus genomic data for the COVID-19 pandemic."
No, this unprecedented on any living and non-living thing that we know.[1]
"In all of this, its worth remembering we've never tracked an epidemic in this much detail before, so perhaps this sort of thing is just par for the course."
We tracked very well the flu during its high season, and influenza genomes are used constant to monitor mutations and other aspects of viral evolution, population genetics and phylogeny.