I don't know about that technique. When I did my initial research on neuroscience of psychotherapy they talked about how memories are actually a neuropathway of several neurons and that the more we revisit a specific memory the stronger that pathway is. Part of psychotherapy creates junctures in those pathways that over time can be stronger than the original memory. This is also a much simplified explanation.

So yes, I believe the brain can rewire itself and I can see how quickly flipping between memories could cause confusing in the neuropathways and possibly breaking the intensity of any (either) pathway. Have you found any downside towards the good memory?

If not, and you are seeing a difference/improvement in when you think of a 'bad memory', it sounds like something is working. I'm not sure how well it would work on a core issue. Some of those seem to be pretty hard to address.