I think they are referring to the point that you want your personal votes to be kept private. Some say it is a form of “cowardice” to not vote publicly.

Personally I see your point is very valid and at least this should be more actively described when signing up for Lemmy and that obviously your instance admins can see everything and you should be very careful (e.g. VPN) if you’d like to participate privately in a conversation. Maybe this is not the right platform for you then ufortunately. Everything in life has its pros and cons and certainly Lemmy is not perfect.