Question AC Adapter Shuts Down

[BR120603]

I left my ASUS AC adapter (adp-90le b) plugged into the wall overnight, but not connected to the laptop (ASUS Vivobook Flip 14). In the morning, I turned on my laptop, then connected the power cable to the laptop. Laptop was not charging. I unplug the AC adapter from the wall and plug it back in and the laptop starts charging. It seems like the power brick goes to sleep if it is not charging the laptop and a power cycle wakes it up. Is this a feature or is this a fault? TIA