According to many, a Davar Gush does not lose it’s heat, and therefore it is not called Eirui Kli Rishon, but Kli Rishon itself.
Granted, IIRC the Mishna Brura brings this svara to require a hot stone to kasher a sink. However, it seems very shver to me.
There is a mefurashe Gemara (Pesachim 75a) that when a hot piece of meat falls onto something it only assers b’kdei klipah because tata’ah gavar. A piece of meat is a davar gush.
No one argues on this Gemara, not Rabbeinu Tam who holds irui kli rishon has the actual din of a kli rishon, and not the Maharshal who holds a davar gush doesn’t lose it’s kli rishon status. They don’t argue with Gemaras.
See YD 105:2 and the nosei keilim. It appears clear that the fact that something retains kli rishon status doesn’t make it capable of assering things below it; that is the halacha of tata’ah gavar. Rather according to these opinions they still maintain their heat in that if something is placed, for example, on top of the davar gush, we will say the thing becomes assur as if the davar gush is still in a kli rishon.
Therefore it seems pashut to me that even if you want to be choshesh for the Maharshal, you don’t have to be choshesh for anything more than klipah anyway. And klipah you can get away – l’shitas Maharshal himself – with irui kli rishon. And we certainly are meikil like this with this klipah of tata’ah gavar which is only a chumra k’mvuar b’poskim.
So I don’t understand the big fuss. It seems to be chumra on top of chumra in the ???? ???? ???? sense.