potent once the infection has started is TOTALLY FALSE.
To be less potent you would have to show a mutation in the virus. That mutation would then have to involve a codon in the mRNA sequence that actually mattered in the protien synthesis. That mutation would also have to cause a structural change in the the amino acid chain to change the structure of the virus. Which most mutations DO NOT. If it did then you would have to show that change infact that would make the virus be less potent. There IS NO EVIDENCE of this AT ALL. To say there is is not responsible.
As of now they have only identified a 10 base pair mutations from the original strand at the greatest. Of course the margin of error in the PCR is likely to be responsible for the majority of those perceived mutations.