In general, I agree with the notion that tacit knowledge is often more important than explicit knowledge - and that it may actually be the very essence of human expertise. However, it seems the author mixes some things up.

First of all, deliberate practice rests to a high degree on a) pre-existing knowledge on the structure of acquiring a skill and b) an established feedback standard that allows to evaluate your performance. These are obviously crucial aspects. If you don't know what characterizes expertise and if you don't know why you're not doing well - then it's difficult to make actual measurable progress. That said, it doesn't mean you can't become an expert at all in a field that does not have those elements currently available. It may just be that you need to put more effort into doing it, seek a mentor known for relevant skills or develop feedback mechanisms to evaluate your performance [1].

Thus, I don't think the distinction made between tacit knowledge and deliberate practice is really helpful. From my understanding, the concepts of "tacit knowledge" and of "deliberative practice" operate on two different levels. Tacit knowledge (or originally tacit knowing) refers to the implicit character of some knowledge. Its counterpart is explicit aka codified knowledge. Conflating deliberative practice with (the acquisition of) explicit knowledge seems counterproductive to me. It seems to me that the author wants to argue that deliberative practice only contributes to explicit knowledge.

I get that explicit knowledge may be needed to create learning environments (and gained before through codification of tacit knowledge) that respond well to the principles of deliberate practice. From my reading of Ericsson that does not mean, however, that deliberate practice only works to build up codified knowledge. Tacit knowledge is in itself a vague concept that is hard to grasp. I wouldn't be confident to assert that building up tacit knowledge happens without building up codified knowledge. Maybe someone knows more about that?

Another aspect of the article that concerns me represents the part about the acquisition of knowledge and expert systems. There seems to be another conflation of concepts. It is referred to Klein who (in reference to humans) warns about the overreliance on fixed procedures for decision-making. I agree with that but nevertheless I'm having a hard time with the argument in the article's context. For me this seems to be more of an argument about having a human making a decision than about the superiority of tacit knowledge over deliberative practice or even codified knowledge applied by a human. I get it, humans can build up tacit knowledge and therefore have an advantage over expert systems in previously unknown situations ... I just don't get the relevance for human acquisition of knowledge here which the article wants to be about.

A similar issue I have with the argument about the scope of deliberative practice and NDM as better alternative. Now I have to say I heard about the term NDM for the first time today (and I'm glad I got introduced, thanks!) but from what's written down in the article, it doesn't really seem to be in conflict with - or even that much qualitatively different compared to - deliberative practice: "you find a master, you work under them for a few years, and you learn the ropes through emulation, feedback, and osmosis". This seems to be possible under the concept of deliberate practice as well.

To get a better understanding, I've read another article from the same author [2] but I'm a bit confused. In the end, NDM just seems to offer more concrete procedures to acquire effective and adaptable mental models (in terms of deliberative practice) that help you to make better decisions. But that can't be the catch of NDM, is it?

[1] I'm currently reading Ericsson's book "Peak" and he mentions the Top Gun academy of the US Air Force as an example for the possibility to develop a "deliberative practice"-like environment.The program was designed to enhance figher pilots' performance by having those pilots surviving the initial air fights in Vietnam to become teachers to new pilots. Establishment of good practices took place through the constant exposure of the teachers to new recruits and constant training on usual fight situations.

[2] https://commoncog.com/blog/putting-mental-models-to-practice...