If a "loophole" remains open for any length of time, it is because the cost of closing it is too high. I consider it an error, if the action does not yield the result intended by the program.

Example AMEX used to have a deal with certain airlines for free upgrades. I got the miles of the upgraded class, instead of the class I bought from AMEX. Loophole or intended result? I never bothered to ask....