So let's see what the Scriptures say regarding salvation.
Eph. 2:8-10; For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, not of works, lest anyone should boast. For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them.
Your claim to salvation that can be potentially lost is a salvation without fruit; it's easy-believism salvation. If there is no consistent fruit production, it's not the true salvation that God Himself has wrought. Read the parable of the seed and the soils again. It's only the seed that sprouts and brings forth fruit that pictures true salvation. Matthew 13:23; "But he who received seed on the good ground is he who hears the word and understands it, who indeed bears fruit and produces: some a hundredfold, some sixty, some thirty.”
You posit a difference between fruitless salvation and salvation God Himself wroughts; as if the fruitless one was a false one not wrought by God.
But the parable of the sower speaks of one sower and one kind of seed. The difference in results came from the type of soil, the difference in peoples and in the walk of their life.
"But he who received the seed on stony places, this is he who hears the word and immediately receives it with joy; yet he has no root in himself, but endures only for a while. For when tribulation or persecution arises because of the word, immediately he stumbles. "
It was received. He endured. He was in Christ! But only for a little while, he did not endure to the end. He is as the branch which was on vine part of Christ but did not produce fruit and then cut off. In Christ and then not.
The branches, they produce fruit by the power of God but God still cuts them off if they won't produce fruit. Just like the parable of the sower and the one who fails to endure persecution, or the one distracted by the cares of the world. They were in Christ. But they did not abide. You say OSAS but Christ undeniably speaks of people saved, and then cast out.
God saves sinners and He guarantees their salvation according to His power.
God grants us salvation by right, it is not earned. It is guaranteed; God won't turn back on His word and Satan can't take it. But it can be lost/rejected by failure to uphold the terms of the agreement.
But to say that once saved one will always be saved, that there is no other possible outcome than for a person to be saved, that God will make is so, that just is not true. That is 180 degrees contrary to what Christ teaches in John; cannot be reconciled. Far from guaranteeing salvation, Jesus guarantees they'll be cast out into the fire if they don't abide in Him.
And what affect do you suppose this will have on peoples eternal destination, telling them their salvation is guaranteed while Christ promises they'll be cast out if they don't produce fruit?
Things like that lead to a sense of inaction, refusals to repent, and indifference. These people are ripe to not yield fruit, to be distracted by the cares of the world, to fall away when faced with temptation, trial and persecution because after all their salvation is guaranteed.
And that makes OSAS a damnable heresy from the pit of hell.