I wouldn't get too carried away with how Paul states things!
Foist of oil, he very tactfully mixes his dire warnings in amongst
his many and copious edifications, exhortations, encouragements, etc.
But, to your point, check this example out ... Hebrews 10:39
"But we are not of those who draw back to perdition,
but of those who believe to the saving of the soul."
Paul has NO idea who amongst his buddies (including himself)
might some day draw back (fall away)!
IF the Holy Spirit told him this,
it would have been an excellent idea to tell us about it.
Then, he wouldn't have guys like me making fun of him.