This would make sense if this were a case of the bare door opening (without door) being too small, which is a case of incorrect specifications.
It’s likely that the retailer would just send it back to the manufacturer for credit, in this case. So they’re out nothing but the overhead of handling that merchandise.
I recall some milk crates sold at a storage store that were listed as 12” did not actually store objects (like records) that were 12”. I don’t think the exterior was 12” end to end either. I know about permitting some allowance of place but it was considerably shorter (as if someone rounded up).