So sorry for the issue @Kryonoglou.
Though, it's not a problem related to the extension. As the Material Extension is the first extension that is a theme for Flarum, you're just seeing this for the first time.
In the future, with themes packed as extensions, this issue will become more popular around Flarum users but as @Ralkage suggested, ReFlar's UnCache extension solves this cache issue easily without those terminal commands.
Many thanks for the interest in the Material Extension ?