Which part? I have already posted the preprint article that states their are at least two strains with one being more infectious. I don't think its questionable at this point that there is more than one strain. As for the differing functions that was why I used the word possible because that hasn't been proven yet.
Here is a study that points out there are at least 2 strains. They name L and S type.
https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwaa036/5775463?searchresult=1
Here is the preprint that claims there are different strains with one being more contagious.
https://www.biorxiv.org/content/10.1101/2020.04.29.069054v1
Another preprint that suggests 30 different strains with some capable of producing higher viral loads than others (up to 270 times higher in some cases). Didn't we discuss a while back how a higher viral load leads to more severe disease? Chuck?
https://www.medrxiv.org/content/10.1101/2020.04.14.20060160v2
Another paper showing 3 different strains.
https://www.pnas.org/content/117/17/9241
There are more if you feel like taking the time to search for them.