Yes, that's an excellent point.  I'll take care of it immediately in the case where the ECO code and the article cover the same opening, like A01 (chess opening) and Larsen's opening.  And if it has a disambiguation function like A00 (chess opening), I'll leave it.  In the case of articles like Sicilian Defense, Dragon Variation, where more than one code is covered, I'll add info about the codes to the article and then create a redirect page.  I'm also planning to create redirect pages like A00 for the codes I've created, though some cases (like B52) will merge with existing info, and others might be un-redirected in the future.