A/A testing is a technique typically only used to test and validate any A/B testing tools or frameworks you are using. It is not something you need to do when using Builder’s built in A/B testing tools. If you do decide to run an A/A test within Builder, keep in mind that it is totally possible you might end up finding a difference in conversion data between the two versions, even though they are identical content wise. This is not necessarily indicative of an error in the A/B testing platform, but is much more likely due to the element of randomness present when testing.
This article by Optimizely explains this in detail: A/A Testing