The classical frequentist interpretation of a confidence interval doesn't require invoking Fisherian hypothesis-testing. It's simply an interval estimate for a population parameter rather than a point estimate, which is semantics close to what he means here. A 95% confidence interval is an interval estimate with 95% coverage probability for the true population parameter, which in the frequentist sense means that it includes the true population parameter in 95% of long-run experiment repetitions. (One can get different kinds of frequentist coverage with a prediction or a tolerance interval, which vary what's being covered and what's being repeated.)
Simple change increased conversion between -12% and 96%
That's not what a confidence interval is. A confidence interval is merely the set of null hypothesis you can't reject.
http://www.bayesianwitch.com/blog/2013/confidence_intervals....
A credible interval (which you only get from Bayesian statistics) is the interval that represents how much you increased the conversion by.