The plugin which bundles the application for Hassio is published once and uses latest tag. Application itself receives regular, tagged, multi-arch updates (https://hub.docker.com/repository/docker/andig/evcc).
Expectation was that Hassio identifies latest has changed and upgrades. Is that correct?
I can not tell you how it is supposed to work, but I am running your addon and it was still on version 0.34 until I deinstalled it and installed it again. Seems like it doesn’t work with “latest”. Also nothing was shown about pending updates.