I have complication images for the Circular image set. According to https://developer.apple.com/design/human-interface-guidelines/watchos/icons-and-images/complication-images/, the Simple size should be 40x40 for the 44m watch. However, adding a 40x40 image leads to an error on Xcode stating that the image should be 36x36 (the same size as 40mm and 42mm). Which is correct?
Xcode 10 GM complication image size doesn't match HIG
I get the same warning.
You should file a bug for this discrepency.
For the time being, you have no other solution than obey to XCode with 36*36. But if you are creating icons, I would advise you to keep also a 40*40, in case.
rdar://44467091