Well yeah. First of all that's another data point that marketing and AI companies can utilise.
Secondly on Reddit only admins could see how you voted and it was communicated that that is the case. In a federated network anyone who is or can pose as an instance can get that data. The Problem is that people assume Lemmy and kBin are more or less just like Reddit and are not considering everyone can get their voting record they assumed was not public. Better not have liked that kinky adult content or that politically controversial post.