While engaging a lost soul do you believe they have a similar understanding of the Gospel as you? How would you know? Is it important to know the depth of their understanding of the Gospel?
Evangelists often lose sight of how much they have grown in the grace and knowledge of the Lord Jesus and thereby assume, perhaps unconsciously, that the lost have a similar understanding.
Of course the lost don’t have a similar understanding. How could they? While they know God exists through creation the depth of that understanding is very limited. Seasoned church goers often have a limited understanding of Scripture and unless someone has extensive interaction with lost souls and thereby a real experience with the nature of unbelief they probably don’t have a similar understanding as the evangelist.
Also, often the lost use words evangelist use, like grace or love, but have a completely different definition since the evangelist’s definition is derived from the Bible and theirs from the world.
So yes it is important to know their understanding of the Gospel if the lost talk to you and you gain that understanding by asking questions. In fact, if you can get them to talk about their beliefs and keep them on track they will clearly confess their views. Then in light of that confession you can address their views.
Information and false teaching is overwhelming and rampant. It’s unrealistic to perceive that lost souls simply living life can sort through it all, develop a clear, in-depth understanding of what they believe and thereby be able to coherently articulate their religious position.
Asking questions allows them to confess this reality to you opening the door for the evangelist to bring clarity to the situation.