Testing for both of those substances has improved, but still leave plenty of room for abuse.
Use of "unknown" or the constant stream newly developed substances is naturally not rigorously studied, but here's a couple of articles referencing the challenges they pose.
Top flight soccer is another sport that's constantly garnering attention for TUEs, but most of the coverage of that is speculative, because other than high level statistics the TUE process is naturally not very transparent (and most of the recent coverage on the topic has been replaced by controversy relating to trans athletes).
