It seems that only supported mobile devices can take advantage of hardware rendering for graphics (for now). Most performance enhancements to Flash Player like this don't require any updates to existing builds. However, the following exception is mentioned in the article you referenced:
... the wmode=opaque or wmode=transparent embed parameters will disable hardware rendering, causing the software to render the graphics.
The layering of Flash content between other content on a page requires the browser to perform the final render composition, which apparently requires Flash Player to send all rendering instructions through the browser instead of directly to the GPU. Therefore, even on mobile devices, Flash content in Splunk will not take advantage of hardware rendering.