Custom blend type issues

[UsernameGeri]

This is an issue I found a long time ago, but basically the custom blend type that uses the Source/Destination Factor and Equation parameters, seems to be kinda totally broken.

Not really sure how to properly put this into words, but the different parameters don't actually do what they're supposed to. Using the Online Visualize Blending Tool, I tried many different combinations using the "add" equation, and all the results were the exact same in-game. This, to be specific:

Here are the two images I tested with on that visualizer tool, you can also try and see the different results you can get. (just copy the image URLs and paste them in on that tool for the foreground and background)

Here's also a testing pack:
blend_test.zip