Mitsubishi publishes detailed specs on all their equipment so if you have the model# and configuration it’s reasonably straightforward to determine what electrical signatures you should be seeing. The cycling pre-heat use is easier to identify above background noise than, say, the constant-on of the controller boards. Variable speed fans and compressors are more difficult for Sense and more difficult for humans to see … it really depends upon whether you (or Sense) can isolate the pattern from other usage. There is, in essence, a “detection cycle” as well. For example, and to state the obvious, Sense is only going to have the potential to detect an HVACs cooling mode in Summer.
The device detection that @nlanzano got is a clear case of the potential for Sense, especially for those among us who want to be lazy after installing Sense and just wait for a notification. The interesting and not necessarily intuitive thing here is that component detection or, indeed, component phenomena detection is not dependent upon a full “device” detection. Sense can take the phenomena in this case and with enough instances determine that it’s likely a “Mini-split left on” and notify you without ever having been able to disaggregate the mini-split with enough confidence to designate it as a device.