score:2
It's not avoiding the DOT rule.
The Argentinian note says that the United terms and conditions apply, which I presume also includes the application of the DOT rule.
The Colombian rules are more permissive than the DOT rule, so by complying with the Colombian law to allow cancellations within 48 hours - United by default also complies with the US law to allow cancellations within 24 hours.
United may keep $50/10%, but we don't know if it does, and in what cases. It is plausible that United does not charge the $50/10% if cancelled within the first 24 hours, but is allowed to charge, according to the law of both countries, if cancelled in the next 24 hours.
Also, it is not clear from the United website if the regional-specific text is intended to replace the main text above, or supplement it. If the latter, then there's no contradiction at all, just statutory notices and expansion of rights according to local law.