Here's the catch:
Adobe has spent much less time on the development of OpenCL GPU acceleration support versus CUDA GPU acceleration support in Premiere Pro to begin with. As a result, its OpenCL performance continues to lag behind its CUDA performance at every hardware price point, except for perhaps the very lowest performance tier.
Secondly, many of the major companies that once supported OpenCL have now either depreciated OpenCL support or stopped supporting that API altogether. And OpenCL itself is now under depreciated, if not discontinued, development. Plus, AMD and Intel have not yet found a Windows-compatible GPGPU API that was expected to replace OpenCL. As a result of all that, it would not be surprising at all that a future version of Premiere Pro would revert completely to software-only MPE rendering for all non-Nvidia GPUs in Windows, with depreciation beginning with the next major version of Premiere Pro (15.x).