I used to handle DSAR requests for one of the big 4, we'd redact the names of other people on joint accounts / mortgages / etc. Obviously the requestor would know these (I hope), but someone elses name is not your personal data. We redacted those names to be compliant with GDPR, so I dont think there's any case here.

If anything the case could be made that sharing the names of who viewed your profile when you pay for premium is a GDPR breach, but I dont use LinkedIn so don't know if theres any way to opt out of this. If there is (i.e private profile), then under GDPR it's fine. Still a bit scummy but like its LinkedIn, its purpose is networking, best route here is not using it, not trying to make the argument that other peoples personal data is yours because its somewhat related.