So I planted potatoes and they have a tick for harvesting, yet I cannot harvest them. I was able to harvest other crops though.
https://clips.twitch.tv/TrustworthyHonestClintmullinsEagleEye-zEAky0PLsCRLsNu1
Replicated by planting harvested potatoes
Replicated by planting harvested potatoes
For reference: Fiber currently unharvestable, but a recent update should have made it no longer appear