> ...since the data can't be linked to people's identities.
Well, 23andMe does "know" the identity of each individual. They know their name, their relatives, a lot about their genetics, and if given consent, store actual dna (biobanking) so that in the future other tests can be run. That's a lot of sensitive information for one entity to own.
Can we assume that 23andMe is at least very competent with security and PII, that they've taken enough safeguards to prevent hackers from stealing the keys to the kingdom? ehh maybe. Can we assume that they won't simply bend over when acquired by another less scrupulous entity? Nope. Can we assume that a future authoritarian government won't simply commandeer data whenever it likes like the CCP already does with Chinese companies? Hell no.
More to the point, however, is that folks are limiting the discussion to information about "individuals". Everyone imagines the consequences of individuals being targeted using this data. But really, geopolitical concerns don't care about individuals (modulo a very small number of key people). They care about populations. So even if individual information is kept safe, there's still awful things a bad actor can do with genetic data from everyone even without identifying individuals. That's what the concern is here.
23andMe has the same ultimate risks as BGI. It's just that BGI has skipped a few steps and gone further along in the dystopian nightmare by virtue of the fact that they're a Chinese company and utterly at the service of the CCP.