Speculation here, but from the article’s description I suspect these are too high in magnitude (they would likely saturate the sensors) and not the right “mode”

Speculation here, but from the article’s description I suspect these are too high in magnitude (they would likely saturate the sensors) and not the right “mode” or frequency. The LIGO method is looking for very small fluctuations in a more complex field (certain components of the “metric tensor” which amounts to measuring tiny time-dependent variations in the speed of light in two different directions). By contrast, this signal would be a change in the direction and strength of gravity’s local pull and is probably one of the things they work hard to filter out at LIGO. As such, the main instrument probably wouldn’t be able to measure them accurately, but I’d expect the instruments used to maintain and isolate the main instrument would see it pretty well. Similar in concept to how a radio antenna isn’t the best way to measure a shift in the local magnetic field. It’s the “same” thing, but the instrument is sensitive to a very different part of the space of “magnetic field changes”, including in this case the fact that the antenna may actually be measuring the field by looking at different data (electric field) and relying on the way the two interact in the “far field”. Edit: sorry for the abuse of scare quotes, I’m on mobile and it’s the easiest way I can think of right now to indicate that I’m oversimplifying certain technical digressions that are deep subjects in their own right