The article is making suggestions while leaving out important information to try to make it seem like this could be common when the data does not support that conclusion.
"What is missed from the media coverage, however, is that these families were identified because member(s) were presenting with conditions that made the researchers suspect a mitochondrial disorder."
"Indeed, the paper discusses this single case, and emphasizes that many attempts in the ensuing 16 years to identify biparental mtDNA inheritance were unsuccessful:"
Slashdot Mirror
I believe a better source can be found on Blaine Bettinger's blog https://thegeneticgenealogist.com/2018/11/26/can-mtdna-really-come-dad/
Which includes the following:
"What is missed from the media coverage, however, is that these families were identified because member(s) were presenting with conditions that made the researchers suspect a mitochondrial disorder."
"Indeed, the paper discusses this single case, and emphasizes that many attempts in the ensuing 16 years to identify biparental mtDNA inheritance were unsuccessful:"