The pech of Tsojcanth

In Lost Caverns of Tsojcanth's upper layer #6's pech are here from elsewhere. I mean, obviously; they sure weren't there in 1975...

In published S4 the pech are digging their way - somewhere. The map says, down; the text and the illo say up, so majority rules. We're not told if these pech're from this system's lower-reaches or from some other network or even another country. We do know as a rule they're not much for surface-travel.

So: they're from below. My choice is the lake west of D.

The pech are the only race capable of using that boat moored at #13 - if we transplant 13 to the ledge between 10 and 11. It's usk-wood, so came from the surface originally. But why wouldn't the pech appreciate the gift that the river gave them.

As for why the pech're prepared to fight the renegade #3 golem (for a fee) but not the other beasties here: one guess, is it was their golem to begin with. Such would be helpful in keeping the giants away whilst the diggers work. It is unlikely to have come up from the lake, so maybe the pech dealt with their fellow Earth-lings, the #18 dao. But you know how those deals go.