Absolutely correct, ET is chassis/converter/gear/etc.
MPH will tell you the story on engine HP. Ever seen cars run crazy MPH for the et? Like 14.30 at 105 ( could be 12.50-12.70), high 11's at 130 (10.10ish), 11.20 at 128 (10.40-10.50). Those numbers reflect a rotten chassis with a decent engine hp.