That's part of the point, though. Ikea might not do separate units, but this is not an uncommon practice elsewhere. In the metric example I don't need rounding

That's part of the point, though. Ikea might not do separate units, but this is not an uncommon practice elsewhere. In the metric example I don't need rounding because I can trivially see 4m 3cm and know it's 403cm. With inches I'd have to do multiplication to handle mixed units.