Vacuum sealing a tin removes very little air. Just enough to keep the lid in place with minimal tin deformation. Packaged pipe tobacco has already been exposed to air for a long time, it doesn’t need more air, once jarred “to get started”.
The problem with oxygen absorbers is that there is still a lot of trapped air in processed tobacco that will never be reached. I’ve thought about flushing jars and tobacco with CO2, but to do that right, you need an anerobic glove box.
In the end, it just isn’t necessary. But it would make for an interesting experiment.