As Thom notes, one problem with mandatory disclosure of information set x is that it seems to preference information set x over information set y. There are many market mechanisms to overcome this distortion, but there are few political mechanisms to do so, and even the market mechanisms are imperfect:

For example, even if non-mandatory information would be more valuable to disclose, disclosure always carries with it a lawsuit risk. At the margin, unless the value of disclosure is greater than the cost, the information won’t be disclosed. For information subject to mandatory disclosure, this calculation is biased in favor of disclosure. Not so for the non-mandatory information. To the extent the mandatory and non-mandatory information sets are substitutes (even imperfect ones), the combination of mandatory disclosure regime and lawsuit risk surely induces some substitution from more-useful to less-useful information.

I do think, though, that there’s a real danger in the government mandating disclosure of an affirmatively misleading figure. There’s a lot of misinformation in the press regarding our purported energy “crisis.” Pressured by worried constituents, governments are scrambling to invest public money in alternative fuels. Unlike venture capitalists, who are motivated by profits and will see through faulty metrics, government “investors” are motivated by constituent pressures. Those pressures are largely influenced by media reports. Journalists are busy folks and will tend to believe (quite rationally, I suppose) that the information in a mandated securities filing is accurate. Thus, we end up with all sorts of news stories about how major oil companies are producing at record levels, while their reported reserves are oh-so-small. Politics takes over from there.

If I may go further, you may ask why information in this form might not happen without regulatory intervention?

I agree with your broader point that if the SEC metric is worthless, it should perhaps be changed.