I have never heard this. I candidly admit that such an interpretation sounds like a bunch of nonsense. No disrespect, DL, but that is my reaction.
Or, and this opinion I argue was that of St. Ambrose, who is generally adduced as a proponent of Baptism of Desire, this BoD can refer to pre-baptized individuals, but in the very sense alluded to by DL.
St. Ambrose in
De Sacramentis explicitly states that even good/devout catechumens cannot be saved if they die without Baptism.
So, does he change his mind in the famous oration about Valentinian? Many people try to argue that. But he makes a very interesting distinction that's overlooked. He hopes that Valentinian may be rewarded for his piety and zeal, and by way of explanation, he says that even martyrs are washed but not crowned, so too he's hoping that Valentinian may receive a washing, but admits that he cannot receive the crown (since not even martyrs receive the crown without the Sacrament).
Recall that there are TWO graces from the Sacrament of Baptism, 1) remission of sin and 2) the Baptismal character. So St. Ambrose appears to be saying that this BoD (like BoB) can obtain the one effect of Baptism, the remission of sin (washing) but not the Baptismal character (crowning).
This crowning was in fact a reference to entering the Kingdom of God, i.e. the Beatific Vision, glory (as it's called by the Greek Fathers).
So we have the dogmatic teaching of St. Sulpicius who states that when in danger of death, the Church must supply the Sacrament of Baptism to catechumens with all haste, lest every single (or each and every) one of them lose ("life and the kingdom") while desiring to receive the Sacrament. Here again, he's saying that even if souls desire Baptism, they cannot obtain "the kingdom"; "life and the kingdom" refers to the supernaturally-elevated new life.
So I hold that there is a BoB/BoD that can remit sin, i.e. can justify, but that it does not suffice for entry into the Kingdom, the Beatific Vision, since it is precisely the character of Baptism that enables human beings to receive this supernatural faculty to see God as He is, a capacity that we lack by nature. I hold that martyrs who would die without the Sacrament would go to a place of perfect natural happiness, i.e. to a Limbo very similar to that of the infants. Those who have BoD, depending on how perfect their desire and contrition are can have UP to a similar complete remission, but also varying degrees short of that.
This again is the distinction between justification (remission of sin) and salvation (entry into the Beatific Vision). While BoD/BoB suffice for the former, it does not for the latter.
For all those who claim that BoD is defined, or de fide, why is it then that we can find no definition of WHAT BoD is, how it works, what it can supply for and what it can't supply for, anywhere in the Magisterium? Why is it that we have as many variations of BoD as there are people who believe in it, the only common denominator being that Baptism is not in fact necessary for salvation (in other words, the lowest common denominator is heresy).
There are in fact several passages in the Church Fathers where they speak of a BoB for someone who's know from elsewhere to have received the Sacrament of Baptism (in one case a priest). So once again the term is being used in the sense of remitting sin.
So this so-called "BoD" and "BoB" ... which I find to be abhorrent expressions (with St. Robert's use of the phrase receiving [the one Sacrament] of Baptism
in voto being much better), as these imply multiple Baptisms and are at least offensive to the pious ears of those who profess ONE Baptism in the Creed. And of course "Desire" is also an attempt to water it down, and extended to pretty much any nice guy, whereas
votum was a very restrictive notion more akin to "vow" or "resolution" ... does this BoD apply to just catechumens, to people with explicit faith in Our Lord and the Holy Trinity, to Jєωs and infidels, even to baptized heretics? Your guess is as good as mine. So when people say we must "believe" in BoD, OK, but we can't "believe in", i.e. "assent to" a phrase or a concept. We can only intellectually assent to propositions. Given that I cannot find WHAT I must purportedly believe about this BoD, how can I give the assent of faith to it?