True, and it's not as bad as their narrower motors. For example the H35 35mm .35mm lam crystalytes were ~85% efficient.
Cromotor ( 50mm ) could hit ~91% peak efficiency and Grin's 45mm fatbike motor can hit 90.1% peak.
Okay, UFO motors aren't so bad, 6.5kg is 14.33lbs, getting 2kw-ish out of...