Before you start throwing out definitions... you first need to determine what the "rules" are for where ever you might be going that requires a "bear canister".
For example, I found the regulations for bear canisters for the Adirondacks that read in part:
I think a bag around an aluminum liner fails that description in two regards:"a commercially made container constructed of solid, non-pliable material manufactured for the specific purpose of resisting entry by bears."
1. The ends of the cylinder are still "sides" of the device and they are not "solid".
2. The liner isn't even a solid cylinder. It's (if like the ursack) a sheet of aluminum rolled up in a cylinder. So that "cylinder" is pliable.