It's not about having conduit right into a round gap - the scaled-down things fits by way of a 20mm gap anyway. It's concerning the conduit remaining near the entrance edge of the box, although the 20mm knockouts getting much even more back - ie nowhere around being according to https://fernandohzncp.bleepblogs.com/37084123/helping-the-others-realize-the-advantages-of-oval-conduit