Are hearts of all $t$-structures on smashing triangulated categories closed with respect to coproducts (also)?
This is Proposition 3.1.2 in the thesis of Parra, "Hearts of $t $-structures which are Grothendieck or module categories".
This is Proposition 3.1.2 in the thesis of Parra, "Hearts of $t $-structures which are Grothendieck or module categories".