Slow charging while screen is on?

I assume that this is on purpose, but has anyone else noticed that their phone, with the stock charger or a QC 2.0 charger, while the screen is on, is locked to a steady charge of ~1040mAh? While the screen is off, it fast charges as is normal.

I assume it's a cap that Samsung put in to make sure the temp of the phone stays low, or something. Unless it's not. In that case, "sigh."

I'm using Ampere to monitor the charge.