Let’s look at the sentence.
The short answer is this: just because diaconate is ordered toward service, that is not a reason that can make it open to women, nor can we say that because not all deacons will become priests, it can be open to women. They might be points to make along the way, but they do not constitute a conclusion.
Now the long answer:
The word “because” is the key. He is suggesting that because the diaconate is ordered toward service, then it might be open to women. That isn’t the issue. The diaconate has ‘always’ been ordered toward service (although we have not always been good about keeping it that way), but has still been always male. There’s nothing new here. Nothing has changed. We do not have al all-male diaconate merely because of a (mistaken) idea that it is only a step toward priesthood, rather we have al all-male diaconate because it has been that way since the Book of Acts, and for other very solid reasons. The diaconate was ordered toward service in Acts, yet it was all male. The diaconate was ordered toward service during the time of the early Councils, yet it was all male.
If there is anything we might call “new” in our understanding, it is that there is one single sacrament of Ordination, which is received in degrees. That was finally settled at Vatican II, even though some are surprised that it took us that long. If can say that we have anything new to contribute to the conversation, it would be to say that since there’s only one sacrament, we must be less inclined towards women deacons.
Now, someone will say that the early Church was unwilling to accept female clergy; that this was their own prejudice rather than Divine Law. That’s nonsense. The fact that we did indeed have deaconesses (albeit unordained) proves the exact opposite, that the early Church was completely willing to have some form of women in ministry, but not the diaconate. Also, much of early Christianity were converted pagans. All of the pagan religions in the Roman Empire had priestesses. Female priests were very familiar to the early Christians, yet they knew that once they became Christian, they had to accept an all male priesthood—and in fact they did.
So, to summarize. There’s really nothing new in the conversation. Nothing has changed. History certainly won’t change.