FWIW, I've tested this patch and it works fine with both KDF as a constructed tag and as a primitive tag.

Please keep in mind, that it is not only about GnuPG and the OpenPGP card, but also between GnuPG and other PGP applications. I'm not really sure what the recent commit is doing, if it only affect the reading or also the writing of the data. But IMHO GnuPG should stick to the standard also if writing the KDF DO data because eventually, it will be used for authentication with the card.