This recent 2016 paper  by Kim is supporting consensus to my model of a modulated biennial forcing to ENSO. I had read some of Kim’s earlier papers  where he introduced the idea of cyclostationary behavior.
The insight that they and I share is that the strictly biennial oscillation is modulated by longer frequencies such that +/- sideband frequencies are created around the 2-year period.
This is not aliasing but essentially a non-aliased frequency modulation of the base cycle. The insight is clarified by Kim with respect to Meehl’s  tropospheric biennial oscillation (TBO).That biennial mode locks the base frequency in place to a seasonal cycle, with the modulation creating what looks like a more chaotic pattern. That’s why ENSO has been so stubborn to analysis, in that the number of Fourier frequencies doubles with each modulating term. Yet in reality it’s likely half as complicated as most scientists have been lead to believe.