The TMRCA calculations need to know approximately how many people were infected to calculate the time. Mutation rate is essentially based on how many people th

The TMRCA calculations need to know approximately how many people were infected to calculate the time. Mutation rate is essentially based on how many people the virus passes between not really time. So if China is lying about the number of infections early on (or even simply doesn't know the true number) then the calculated time of first infection would be off.