Remember, at this time you have to actively opt in for your DNA to be usable

While that may be the case, I think the harrowing aspect of it is that the person using the service is essentially "opting in" for anyone related to them. On the one hand of course if you have nothing to hide, what's the big deal? But it definitely is still giving me pause that people are being identified through DNA that they had no control over being added to a database.

I work in a genetics lab myself doing health-related research, and maybe I've watched too much Black Mirror but to my knowledge there's not currently much stopping a future health insurance provider from saying "Well, your sister wanted to know her ancestry so now we know that your family has high genetic susceptibility to breast cancer so we're gonna go ahead and charge you more based on the risk we are taking on."

(I AM NOT A POLICY EXPERT and this may just be paranoia, but it's in my brain all the same. Your genes can say so much about you, and a huge portion of your genetic material can be given to who knows who without any say from you by way of family giving their DNA.)