Function solid_model_scale 

pub fn solid_model_scale(solid: &BrepSolid) -> f64

model_scale of a solid’s vertices — the RAW bounding-box diagonal, with no >= 1.0 floor. This is what direct-edit wants: a sub-unit part must keep sub-unit bands. (BrepSolid::validate wants the same thing and still hand-rolls it, for the reason its own comment gives — it answers 0.0, not 1.0, for a vertexless solid. Reconciling that contract is a follow-up, not a free ride-along.) Use solid_scale for the floored variant the tolerance policy is built on.