No, but here's why.
Biblical Unitarianism is Christian - they believe in a God, creator of all things, His son Jesus and the holy spirit.
They believe in the salvation plan the bible outlines and that it is only possible in and through the name of Jesus and trusting in his sacrifice for all sin.
This arrangement is offered by God through His grace. There is no salvation that men can earn or expect to receive by any 'good works' or law keeping.
God knows the broken and corrupted nature of all men. He knows the cause of it (the devil) and has provided the remedy for it in Jesus.
When we die in this life, we will all die with many wrong understandings and false beliefs - we can never be 100% correct. The deception that has been foisted onto the world includes religious confusion resulting in myriad religions and Christian denominations.
God is well aware of all this and it is entirely covered by the bold paragraph.
If a believer (in God) dies believing a 3in1 God, they have two possible futures.
- God has deemed them a 'saint' and will be raised to meet Christ at his return. This is regardless of their 3in1 understanding/belief, but of their faithful living according to the calling God has placed on their life.
- They will be raised in the second resurrection with all others to finally know the true God and the salvation offering in Christ.
The very concept of whether a man's teaching/biblical interpretation has any bearing on the salvation God offers through grace via His son is abhorrent. Man has nothing to do with this core process by which God desires for 'all men to be saved'.
For a general overview of salvation as outlined above: Becoming a Christian: Why? What? How? (Biblical Unitarian)