Usually when the release notes say something like this, it’s because the details are fairly technical and uninteresting to the average person. This release included a workaround for an AMD bug that caused diagonal texture artifacts on RX 500 and Vega series GPUs (and possibly other AMD GPUs based on the GCN architecture) on Windows. A performance-improving side-effect of the workaround for this bug was a reduction in the amount of memory bandwidth required of “immediate mode” rendering hardware (ie: most non-mobile GPUs).
As for blending precision, this build included a change to the pixel format used for the intermediate render target that is required for some GPUs/platforms. When we first shipped 1.7, we were rendering to sRGB-encoded targets when required. We discovered that some hardware was particularly bad at blending in this color space, resulting in inaccurate visual output, so we switched to using either a 10 or 16 bit-per-channel linear texture format instead (depending on how capable we think the GPU is). We still use sRGB for cases where it’s needed as part of a workaround for platform or GPU deficiencies on certain Android devices, but loss of blending precision doesn’t seem to be a problem in these cases due to the architecture of tile-based mobile GPUs.