Translating Exodus 19:9 (Robert Alter and the Cloud)

I've been working my way through Robert Alter's work, The Art of Biblical Translation. He has a number of interesting analyses pertaining to biblical translation and Hebrew philology. One example that he gives of so-called biblical inaccuracies is Exodus 19:9. Notice how some translations render this passage and specifically, what they state about the cloud:

Exodus 19:9 (ASV): "And Jehovah said unto Moses, Lo, I come unto thee in a thick cloud, that the people may hear when I speak with thee, and may also believe thee for ever. And Moses told the words of the people unto Jehovah."

Exodus 19:9 (CJB): "ADONAI said to Moshe, 'See, I am coming to you in a thick cloud, so that the people will be able to hear when I speak with you and also to trust in you forever.' Moshe had told ADONAI what the people had said;"

Exodus 19:9 (CSB): "The Lord said to Moses, 'I am going to come to you in a dense cloud, so that the people will hear when I speak with you and will always believe you.' Then Moses reported the people's words to the Lord."

Exodus 19:9 (ESV) " And the LORD said to Moses, 'Behold, I am coming to you in a thick cloud, that the people may hear when I speak with you, and may also believe you forever.' When Moses told the words of the people to the LORD,"

Exodus 19:9 (RHE): "The Lord said to him: Lo, now will I come to thee in the darkness of a cloud, that the people may hear me speaking to thee, and may believe thee for ever. And Moses told the words of the people to the Lord."

NET Bible: "The Lord said to Moses, 'I am going to come^[r] to you in a dense cloud,^[s] so that the people may hear when I speak with you and so that they will always believe in you.'^[t] And Moses told the words of the people to the Lord."

note [s]: tn Heb “the thickness of the cloud”; KJV, ASV, NASB, NCV, TEV, CEV, NLT “in a thick cloud.”

As NET informs us, I found that most English Bibles say some version of "thick cloud."

NWT 2013: "And Jehovah said to Moses: 'Look! I am coming to you in a dark cloud, so that the people may hear when I speak with you and so that they may always put faith in you as well.' Then Moses reported the words of the people to Jehovah."

First, Robert Alter relates that "A rough equivalent in English of the literal effect would be 'the thunderhead of the cloud.' "

Then, contrary to all of the foregoing Bibles, Alter writes: "so I propose rendering it as 'the utmost cloud.' The mistaken construction of ‘av as 'thick' does not entirely alter the moment, but it takes away something of its high solemnity."

He encourages Bible translators to consult Exodus 10:22 and think about the setting for the verse. To close, I've read five reviews of Alter's work, and have yet to find a scholar who criticizes "the utmost cloud." But frankly, I need to do more research on this issue.