You're talking about 'transparency' in the accountability context. Transparency of voting, transparency of public posting history etc. I'm referring to it terms of honesty from the developer here about what they want, and reading into what the audience wants and why they want it.
Every site has to make some balance between privacy and transparency for its userbase. If the majority of a website audience does want some interaction on the site to be private, to be obfuscated, something that if made private would have consequences to the sites operations - then that's what they want. I think it would be bad if Rimu just said "screw everyone, I'll do what I like" and overruled the prevailing opinion.
But in any case, as I said, your criticism is not of piefed here but piefed.social as other instances could have always just implemented public voting entirely regardless of what piefed.social chose to do.