This image is derived from the "yellow bananas" texture at https://www.manytextures.com/ (for details and licensing see the 4096x4096 PNG version at https://www.manytextures.com/texture/258/yellow-bananas/).
The main aspect of the conversion to allRGB performed here is that when differentiating among non-unique colours the algorithm changes them in a way to keep them closer to the colours of neighbouring pixels.
As a result, besides colour differences being amplified, colours also tend to spill across pixels, instead of dithering.
This usually results in derived images with colours that look exaggerated and disruptive, however as an exception, this particular image looks both colourful and relatively smooth.
