
I would limit 'badge engineering' labels to vehicles where (essentially) if you were to take the front and rear clips off, the balance of the body and interior is essentially identical and perhaps some mechanical mods - G5/Cobalt, Civic/CSX etc.
The ES, TL, and A3 may all have a common base - aka platform sharing - but everything else intrinsic to the brand is specific and distictive.
You'd never mistake a Volvo S40 for a Mazda 3, but they share DNA, for example, and at 5 paces the Civic and CSX are largely indistinguishable save the 'badges'. And Honda has done a great job blurring the lines in the badge with their "H" come "A" logo.
Not necessarily a Websters Dictionary definition, but my 2 cents.