Playing Splatoon 2 Over LAN Gives You A Built-In Voice Chat

According to a NeoGAF user, PetrCobra, who discovered something in regards to voice chat in Splatoon 2. It’s related to a local connection where “you are all connected to the same router and you press a button combination (I think it’s L+R+Left stick). It then uses the router in a LAN configuration”. According to PetrCobra, they tried this out in a pub game of Splatoon 2 last week. They said that “one of us had a microphone on his headphones, and the second we switched into the LAN lobby we heard what he was saying very loudly in our speakers”. By doing so, they discovered that a LAN connection can give players a built-in voice chat with no app required. It can only be done with this method, but it does indicate that a built-in voice chat is in the game in some form. So Nintendo wants you to use an app, while developers put in built in voice chat. Sounds super fishy to me. Thoughts ?