CIFilter/CIContext gives different results on Simulator and Device - ios

Question

I am using (relatively) simple filters on ios using coreimage.
However, on the Simulator I get my expected results but the device gives slightly different output.
The filter causing the issue is CIEdgeWork. But it is combined with some other filters.
The code just adds a set of CIFilters to a CIImage (created by loading PNG data).
The filters are; CIColorClamp -> CIColorInvert -> Composited over CIConstantColorGenerator (white) -> CIEdgeWork
The resulting CIImage is rendered out using CIContext.pngRepresentation(…) and displayed in a UIImageView.
Outputting the debug descriptions of the CIImage shows only one (minor?) difference.
Simulator
<CIImage: 0x600000ae4d20 extent [0 0 240 240]>
crop [0 0 240 240] extent=[0 0 240 240]
colorkernel _edgeWorkContrast(src,contrast=15.3272) extent=[infinite]
kernel _cubicUpsample10(src,scale=[0.25 0.25 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[1 4 0 1]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[4 1 1 0]) extent=[infinite]
colorkernel _edgeWork(src,blurred) extent=[infinite]
colorkernel _srcOver(src,dst) extent=[infinite] <0>
premultiply extent=[0 0 240 240]
colorkernel _colorClampAP(c,lo=[0 0 0 0],hi=[0 0 0 1]) extent=[0 0 240 240]
unpremultiply extent=[0 0 240 240]
affine [1 0 0 -1 0 240] extent=[0 0 240 240]
colormatch "sRGB IEC61966-2.1"_to_workingspace extent=[0 0 240 240]
IOSurface 0x6000033ec410(1) seed:0 RGBA8 alpha_unpremul extent=[0 0 240 240]
fill [1 1 1 1 devicergb] extent=[infinite][0 0 1 1] opaque
kernel _cubicUpsample10(src,scale=[0.25 0.25 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[1 4 0 1]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[4 1 1 0]) extent=[infinite]
<0>
Device
<CIImage: 0x280743ba0 extent [0 0 240 240]>
crop [0 0 240 240] extent=[0 0 240 240]
colorkernel _edgeWorkContrast(src,contrast=15.3272) extent=[infinite]
kernel _cubicUpsample10(src,scale=[0.25 0.25 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[1 4 0 1]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[4 1 1 0]) extent=[infinite]
colorkernel _edgeWork(src,blurred) extent=[infinite]
colorkernel _srcOver(src,dst) extent=[infinite] <0>
premultiply extent=[0 0 240 240]
colorkernel _colorClampAP(c,lo=[0 0 0 0],hi=[0 0 0 1]) extent=[0 0 240 240]
unpremultiply extent=[0 0 240 240]
affine [1 0 0 -1 0 240] extent=[0 0 240 240]
colormatch "sRGB IEC61966-2.1"_to_workingspace extent=[0 0 240 240]
IOSurface 0x28074d5c0(70) seed:1 RGBA8 extent=[0 0 240 240]
fill [1 1 1 1 devicergb] extent=[infinite][0 0 1 1] opaque
kernel _cubicUpsample10(src,scale=[0.25 0.25 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianBlur3(src,offset0=[0 0 0 0]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[1 4 0 1]) extent=[infinite]
kernel _gaussianReduce4(src,scale=[4 1 1 0]) extent=[infinite]
<0>
The lines that differ are:
Simulator
IOSurface 0x6000033ec410(1) seed:0 RGBA8 alpha_unpremul extent=[0 0 240 240]
Device
IOSurface 0x28074d5c0(70) seed:1 RGBA8 extent=[0 0 240 240]
I don't know enough about graphics to say if this will have an effect.
What did I try?
My first (uneducated) guess was the simulator was using CPU and the Device was using GPU. So, using this code to try and force the device to use the CPU (it had no effect):
// ... Create CIImage with filters, set to `outputCIImage`
guard let colourSpace = CGColorSpace(name: CGColorSpace.sRGB) else { throw RenderError.failedToCreateColourSpace }
let context = CIContext(options: [CIContextOption.useSoftwareRenderer : true])
guard let png = context.pngRepresentation(of: outputCIImage, format: .RGBA8, colorSpace: colourSpace, options: [:]) else { throw RenderError.failedToCreatePNGData }
// ... return `png` as Data, then used in `UIImage(data: ...)`