This is surely more optimal if you do the statistics right? I mean I'm sure they didn't but the intuition that you can stop once there's sufficient evidence is correct.
Bear in mind many people aren’t doing the statistics right.
I’m not an expert but my understanding is that it’s doable if you’re calculating the correct MDE based on the observed sample size, though not ideal (because sometimes the observed sample is too small and there’s no way round that).
I suspect the problem comes when people don’t adjust the MDE properly for the smaller sample. Tools help but you’ve gotta know about them and use them ;)
Personally I’d prefer to avoid this and be a bit more strict due to something a PM once said: “If you torture the data long enough, it’ll show you what you want to see.”
