Ok. So the method name is super misleading. onChange suggest that it actually react to changes. onLoad would be much better name.
BTW its super weird design choice made by Twitch dev team to not broadcasting configuration changes by default. In 99% of cases extensions need to have up-to-date configuration, which means in 99% of cases developers’ll have to use Pub/Sub anyway and implement this by their own.
Thanks for the reply.