It was AMD in particular who was battered by all of this work, with the discovery that both their single-GPU and multi-GPU products were experiencing poor frame pacing at times. AMD could meet (and beat) NVIDIA on frame rates, only to lose out on smoothness as a result of poor frame pacing.
Since then we have seen both some progress and some new revelations on these matters. AMD was very quick to start working on resolving their single-GPU issues, and by March when they were willing and able to fully engage the tech community, they had already solved the bulk of those single-GPU issues. With those issues behind them, they also laid out a plan to tackle the more complex issue of multi-GPU frame pacing, which would involve spending a few months to write a new frame pacing mechanism for their cards.