Most mainstream kernels store geometry in meters even when your document units are mm or inches — SolidWorks will show a 1.00 mm edge but it’s 0.001 m internally. Have you seen a production system that truly computes in inches, and did its absolute/relative tolerance scheme impact fillet/offset robustness or STEP scaling?
Haven’t seen a modern kernel that truly “computes in inches”; even inch templates usually normalize internally and only express absolute tol in part units. The gotcha I’ve hit is leaving 0.001 in on tiny parts — fillets/offsets get brittle and STEP carries inches but preserves those too-tight edges; tie tol to bounding box or use a relative scheme (unit wars are pizza-slice math). Which kernel are you thinking of?
Creo/ProE computes in the model’s units, so not like SolidWorks’ “0.001 m internally,” and its Absolute vs Relative Accuracy flips fillet/offset robustness; on inch parts, 0.0001 in Absolute made small blends fail, switching to Relative stabilized it across sizes. STEP AP242 keeps units so scaling’s fine, but importers that hold a fixed meter‑based absolute tol will misfit inch geometry unless you pre‑tighten before export.