The problem here is comparing apples (with sugar glaze) to pears (with cream) – that simply cannot be transparent.
The wall planned so far is "complete" in the sense that no additional wall shell is needed. Therefore, the supplier logically suggests not presenting a full masonry shell there – and thus actually an "excess" – but alternatively to use a full brick layer on the complete wall instead of the clinker veneer layer, and then place this in front of a multi-shell wall accordingly.
I question this measure in its intention and especially in its extent if the builder is reportedly only after the optical effect for which the sliced clinker serves its purpose qualitatively fully. So much for the partial question of whether the effort of the "clinker" full shell is necessary or even in any way superior: clearly "no" in both technical and qualitative terms.
The second aspect of the question is whether to follow the proposal of the alternative wall construction. And here, atypically, not the same construction material is suggested in a thinner thickness for the then only "inside" wall shell, but a system change to a construction wall shell of the type "insulating foam block".
But this is a profound change with, from my point of view, three disadvantages:
1. it is inappropriately complex for the desired outcome, without any worthwhile benefit;
2. it requires personnel with completely different processing experience for both wall shells (and in my expectation is also not neutral with respect to statics in the sense that the calculations would have to be different);
3. it makes the comparison difficult for the lay builder to evaluate competently on their own terms.
In particular, point 3 would be the decisive argument for rejection for me, no matter how nearly price-neutral the switch might be.