Main Cabin Extra was implemented on Feb 1st 2018 and was limited to the bulkhead and exit row seats until planes could be reconfigured to add MCE rows at the front of the economy cabin. These new config planes and the added perks associated started in service on June 5th of this year. It will be expanded as planes are reconfigured.

My January 2019 flights were of the bulkhead and exit row variety ...