Yes, that was precisely my point: a mix of EUV and DUV is used because the upper layers don't need EUV and DUV is cheaper and more mature.

Furthermore, it seems likely that the uppermost layers will never use EUV and that therefore a mix of EUV and DUV will always be used, indefinitely. This seems likely unless EUV surprisingly becomes much cheaper so that unifying on a single technology becomes worth it, or unless both EUV and DUV are replaced by something else entirely.