According to Vicflora, the leaf of ixioides is 'filiform to linear-lanceolate, 8–30 cm long, 5–10 mm wide, canaliculate to plicate or inrolled distally, dark green, often reddish at base.' Seems pretty variable!
In that case we should overhaul the taxonomy and consolidate all sun orchids into a single category: Thelymitra sp. I am in favour of this proposed change.