More than likely, no.
More than likely, yes.
Just like there was a point in time when DDT was considered safe or that dumping oil/gasoline/or kerosene into lakes and ponds was a good idea (decreases water tension thus destroying mosquito breeding grounds), and since formaldehyde has a classified for-use as a disinfectant, it is plausible that formaldehyde was once used to sanitize cans.
Your assessment may be possible but it is also possible that more what the evidence says to the contrary people are going to believe what they believe.
Aldehydes are often used as flavoring compounds, both natural and synthetic. It is understood that aldehydes are formed at some point during the beer making process, and it is generally thought they contribute to the background taste of beer, but to what extent is currently not known. It is currently thought that these aldehydes bond to other molecules and as such mask their own unique tastes. It is also currently thought that these aldehydes eventually release themselves as beers age to which they contribute to a "staling" of the beer. Beers like Bud are "designed" and meant to be drunk as soon after production as possible, perhaps to avoid detection of these aldehydes.
It could also be, that because of the release of aldehydes in "old" beer, that rumors such as Bud has formaldehyde, Corona has formaldehyde, Heineken has formaldehyde, and so on get their start.
It would be interesting to age a can of Bud for 3 or 4 years, then to analyze its contents.
I don't doubt that Bud gives some people headaches. For what-ever reason Pabst upsets my stomach in ways that no other beer does. The upset stomach I am talking about is the next morning...on the toilet... It's only Pabst that does that to me suggesting that something is in Pabst that is not in other beers I drink or have once consumed.
This is an interesting topic. Anheuser-Busch claims that "... the majority of our products are brewed without any artificial ingredients, additives, or preservatives" but they make no indiction which ones are or what the artificial ingredients, additives, or preservatives may be. AB does claim that tannins are used as an anti-haze agent in Bud, and that these tannins are removed prior to bottling. Perhaps this what induces the headaches?
Then I found this:
https://www.homebrewtalk.com/f14/chemical-additives-commercial-beers-21378/
