I understand the reasoning and the explanation but it's not always best to transfer terminology from one document to another without some caution. Some paraphrased observations I'm sure you have thoughts about:
- Rom1:19 speaks of the [things] known of/about God
- Rom1:20 says God's power and divinity are seen and understood
- Rom1:21 says they knew God sufficiently to glorify and be thankful to Him
- This is the same word used in John17 and I note that John17 speaks of knowing God and Jesus Christ so there is more known here
- Rom1:28 says they did not value to have God in knowledge - this knowledge is experiential knowledge - knowledge meant to be utilized - so it seems to elaborate what knowledge of God / knowing God they had
- Rom1:32 says they have this experiential knowledge of God's righteous judgment of death.
They know God. Not as John is speaking about knowing God, but they know God.
I'm sure you also know that John will take his concept re: knowing God into parallels with loving and obeying God.