This topic always opens a can of worms. Best i can say is read the thread i linked to a few posts ago. It's long but eye opening.
In a nutshell, oxidation occurs extremely rapidly in the mash. Untreated mash water has more than enough dissolved O2 to oxidize a mash within a matter of minutes. This results in permanent loss of certain flavors. The resulting beer isn't bad, but it is missing something it could have had. If you preserve the flavors in the mash, you can still lose them later on if your process doesn't exclude O2. However, if you oxidized your mash, like Brulosopher did, then you didn't have anything to preserve, thus all of his splashing after the fact was for naught.
I've used the LoDO process on my last 6 batches and i can confirm when executed correctly there is an extremely noticeable difference in the mash - it's odorless (meaning compounds haven't been volatilized and driven off) and the resulting flavor of the wort is very different in a good way.