I think that such systems are not all that uncommon. For instance, there are systems that monitor the noise level of bearings, not because anyone might care about noise, but because bearing noise is easier to monitor than is bearing wear. So when a certain noise level and/or noise spectrum is reached, the monitoring system raises an alarm.

So, "If the specified threshold noise level/spectrum is measured, it must mean that bearing wear has reached x and must be replaced."

I suppose one could say the same thing about, say, monitoring the weather, or many other things. If the air pressure is x, and it is falling at a rate of y, then it must be true that we have a severe weather front approaching.

If this condition is true, then it must follow that this cause is true, going from effect to cause. Which may just be the easier direction to go, for practical reasons.