I have to weigh in with qhrumphf, there is o2 in co2. Once I confirmed this from my co² supplier years ago, I switched to carbing with sugar. Stopped the major o2 contamination. Most important on beers I keep for months/years.
I still use bottles to purge and and transfer most beers. I am going to change my lager discharge from fermenting to purge kegs.
It did make a minor stability improvements when I started natural carbonation on my kegs, not to the typical cardboard flavors but the, early oxidation notes, light delicate robbing of character that puts the beer on the BOS table.
This is super annal worry issue. Lots of issues to address prior, and as mentioned, drink it quicker to prevent the issue. I like to worry about better beer and keep chasing the perfect pint.