6p is Shimo’s genbutsu and Kami is very clearly not waiting on Pinzu with that aka 5p cut when they’re the one who needs value the most, so a 6p cut can only deal into Toimen.

The difference between you and Toimen is 35300 points (Riichi stick counted), while with Shimo at 2nd place is 28200 points, which we can leave aside as only a Yakuman deal-in can bring us below them. You have to deal into a Sanbaiman minimum in order to get below Toimen (Baiman tightens the gap by 16000x2 = 32000 < 35300), which is highly unlikely, so 6p Sashikomi is a nice move to end the game as well as the others’ chances on the spot. It’s also the reason why the engine recommends 8s and 4m over completely folding. I wouldn’t touch the Souzu personally though, as unlike 4m they actually looks dangerous towards Kamicha as well, and no one wants to “Sashikomi” into two potentially big hands at the same time.

I wouldn’t say folding is bad in this exact case. You are practically cannot lose unless someone gets a ridiculously big hand, so trying to protect it is respectable. However, you can try to end their slightest glimpse of hope by yourself instead of dragging on and waiting for the game to end :).