Each display runs at its own resolution, whenever it was connected
A display could run at the resolution of one connected months earlier, and a display added later wasn't set up to mirror the first.
A player worked out its display setup once and then kept it. Whatever was plugged in the first time set the resolution: a 4K display installed this month could run at 1600x900 because a 1600x900 display had been on the end of that cable 6 months ago. A second display added after that first look was never set up, so it didn't mirror the first one.
Players now read the displays that are actually connected. Each one gets its own preferred resolution, and a second display mirrors the first, whichever order they were plugged in. 2 displays with different resolutions now both show the whole picture, instead of 1 of them showing it cropped.
If a display at one of your sites has looked soft, or a second display hasn't shown the same picture as the first, this release fixes it.