Kind of like how driving in a beat up Yugo is better than riding on a yellow school bus configured for tiny Kindergarden students...

To the OP's question ... if memory serves, AC forbids any and all upgrades to J (or even Rouge wanna-be J) on Aeroplan tickets. IIRC, if you used points for your flight, you won't even be offered the chance to buy a paid upgrade.

And AC's paid upgrade costs - when it is offered - tend to be far, far higher than US carriers. (For domestic and crossborder, I've often seen the upgrade cost about the same as buying a Tango fare (minus taxes/fees/surcharges) for the same segment.)