EV highway boost confuses ScanGauge

The merge onto the highway this morning was with the usual 1500 RPM maximum, dramatically increasing MPG from the usual 30 to 90 by taking full advantage of the plug-supplied electicity.

Upon settling down to a steady cruise at 70 mph with an engine RPM at only idle speed, still drawing heavily from the plug-in battery-pack, I noticed the instant MPG on my ScanGauge. 21.7 MPG! Huh?

The instant MPG on the Prius speedometer was spiked at 100 and so were the minute-summaries on the Consumption screen.

The ScanGauge MPG value kept jumping from a low in the 20's to the 80's & 90's. It clearly didn't understand what was happening.

Is anyone else seeing older devices struggling to properly report data from new technology?