red/blue swap (Gimp 2.9)

[E_T]

I'm trying our IR photography and use Lightroom, but I've been using Gimp to swap the red and blue channels.  Works great, but I noticed that it doesn't seem to work right if I export the image from LR in Adobe Pro RGB colorspace.  When I do this, and swap the colors in Gimp, they look off.  The sky should be blue, but it looks more blue/green.

If I export the image in sRGB, the swap works as it should.  Any idea why this happens?