The issue at hand is whether Okrand wrote that description accurately, intending it to be pronounced as the glide between two sounds that a linguist would recognize in a typical American pronunciation of the word “oh” that rhymes with “mow”, or if he was merely making sure that you would never use the “o” sound in “pot”, which is the Klingon {a} sound.

No, the issue at hand is that TKD says ow is indistinguishable from o and uw is indistinguishable from u, but aw, ew, and Iw are said to be different from a, e, and w, and are described as diphthongs, even if that word isn't used.

Maybe o and ow are a single phoneme in Klingon — they don't distinguish between the monophthong and diphthong vowels. Maybe word-final o is different from word-internal o. Maybe the text of TKD is just plain wrong and Klingons would pronounce no exactly the same way you say it in Italian, [o]. Maybe o is always a diphthong and Okrand just mispronounces it sometimes.

I don't know what the correct answer is. I just know that it's not as simple as "Klingon o is [o]. End of story." If Klingon o is just [o], the text of TKD must be explained in that context.

Meanwhile, in recordings of Okrand speaking Klingon,

Which, some have argued, he pronounces with an American accent. For instance, he uses an untrilled r when he says rgh, which isn't described in the dictionary. He has himself said he doesn't necessarily follow his own instructions in pronunciation.

there is no second vowel sound in {o}.

Except sometimes there is.

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SuStel
http://trimboli.name