I don't think there is much hope for reconstructing what the instructor was talking about based on your recollection, and asking him is your best bet. However, there is a somewhat well-known fact that the same thing can have multiple causes. This is especially true of the so-called ATR vowel distinction, between involving pairs like i/ɪ, e/ɛ, o/ɔ. This distinction exists in many languages of the world (not in any Nordic language), and it has been determined empirically that the articulation of that distinction is not identical across languages. There are in fact many articulatory primitives that can be combined to create this distinction, and languages differ in their exact recipe for making these vowels. (This is a topic that has been researched since Lindau in the early 70's). At the time there may have been some sense of "discovery" that Akan ATR and Kalenjin ATR are different, but that is probably because nobody has worked on both Akan and Kalenjin at the same time.
The question that should be asked is, in what sense is the distinction [u/ʊ] as observed in Somali, Akan, Kikuyu, Teso and Mongolian "the same", when they are physically produced differently? The answer usually given by phonologists is that the sameness comes from reflecting the same cognitive thing (the feature ATR), and that ATR is not a precise description of how a vowel is produced, it is "just precise enough".
Given the standard distinctions that are made in place and manner of articulation, a description like "back high unrounded vowel" only identifies a neighborhood, and languages with [ɯ] can pronounce that vowel in lots of different ways. IPA letters and their corresponding articulatory descriptions have low-to-medium granularity in terms of describing exactly how a sound is produced in a language.
If you want something Nordic, in Norwegian the letter "o" is somewhat ambiguous in representing /u/ and /o/ (which in turn both have variants depending on context). For example the name Ove is pronounced [uve] and the verb sleep "sove" is [sove]. But this fact has been known for a long time.