A numerical survey of the plasma response in ASDEX Upgrade ELM control experiments is conducted, to clarify the role of triangularity in the suppression mechanism. The pedestal pressure increases with triangularity consistent with previous work , which modestly boosts the peeling response. However, the peeling response decreases with increasing triangularity due to an increase in the gap between the coils and plasma, reducing the effective applied field. Consequently the peeling response is found to be lower in high triangularity and ELM suppression, than low triangularity and ELM mitigated phases. Therefore the hypothesis that the requirement of high triangularity is due to the requirement of a sufficiently large peeling response is not likely to be correct. An alternative hypothesis is discussed, that high triangularity is required to access suppression because the associated enhanced pedestal stability allows the edge deformation to be large enough to control the density, without the reduction in stability due to boundary deformation destabilising ELMs. To rephrase, it is supposed that in low triangularity, the mitigation mechanism precludes suppression, while in high triangularity it does not. Results here are consistent with this hypothesis, however the tools required to test it are currently lacking and must be developed.