Yes, I am fully aware that your sources mention implicit baptism by desire

I simply wanted to go into deeper detail about what
implicit actually means. It is one thing using the word, another explaining its meaning.
We cannot judge others. Only God can. The only ones who cannot attain to salvation are those “who care little for truth”. We cannot possibly know whether an atheist has ardently searched after truth and failed to find it or not. Really its a moot topic. All we can do is state the fact that the church leaves it as a possibility. The possibility does exist for those who do not believe in God still to attain to salvation.
I think you would do well to remember Blessed Pius IX’s words:
Pius resolutely refuses to set definitive limits to the application of “invincible ignorance”. To this end I will not set limits since I can never fully understand the underlying psychological, social, moral or even physical factors which influence people. I thus cannot simplify human nature. I cannot judge a person who may genuinely have searched after truth and tried to inform his conscience but, for whatever vast number of reasons, still has an erroneous conscience and is bound to follow that conscience.
In this vein Pope Pius XI was so bold as to proclaim to one of his Cardinals who was going on a diplomatic visit to Libya:
I think we do a great disservice to our Lord to “set the parameters” of his mercy. Lets just admit the possibility yet equally stress the essential membership of the church, whether formally or more imperfectly spiritually, for salvation - EENS (no salvation outside the church).
What you cannot undermine is the frequency with which conscience can err, even with a flood of information and genuine seeking. The media preaches so much contrary to natural law, that conscience’s voice can be considerably dulled and people are left in great confusion. I think the modern world has caused more confusion and less culpability, the opposite from yourself:
As Vatican II teaches: “
Conscience frequently errs from invincible ignorance without losing its dignity. The same cannot be said when someone cares but little for truth and goodness, and conscience by degrees grows practically sightless as a result of a practice of sinning” (Gaudium et Spes)
How can we know if an atheist “cares little for truth”? We cannot get inside his head. Its impossible. Saint Edith Stein (Teresia Benedicta of the Cross) once noted:
Back in the 40s, their were these great and very orthodox priests who held an American Catholic talk show on radio by the name of Rumble and Carty. Read this transcript, its about Judaism but its points are somewhat applicable here too:
I don’t think we’re actually “at odds” greatly. We are both sincere Catholics looking at the same doctrine and many similar sources but reaching somewhat nuanced interpretations from each other. I can only state it as I see it, as can you.
I leave it for others to decide which one of us is closer to the truth