VideoCardz points out that new Linux patches from AMD reveal that both the Navy Flounder and Sienna Cichlid GPUs share the GFX1030 id. It's uncommon for two different AMD GPUs to use the same id. Sienna Cichlid is the upcoming "Big Navi" GPU but it's still unknown what Navy Flounder is.
Historically speaking, only some GPUs from the same generation shared the GFX level. The most recent being: Fiji, Polaris10, and Polaris 11 (GFX803). Both Vega and Navi have IDs for each GPUs. Since we already know IDs for Navi 22 (1032) and Navi 23 (1033), Navy Flounder could either be a variant of Sienna Cichlid or a completely different GPU.