A question as big as the Pacific Ocean!!!!
Personally, I do not believe in learning done in "phases," just as I do not believe that one should speak of interpretation after a certain period of study. Even a tiny piece of Beyer can be an object of interpretative study (the search for meaning).
Personally, I do not believe in the "separate" meanings of the terms: "Technique," "Interpretation," and "Reading the Score and/or sheet music."
I am a supporter of Gestalt Theory, in the part where it states: "The whole is not the sum of its parts." In fact, the "whole" is something more. It is the whole. I think that in Art, and not only in Music, one must not lose sight of the "whole" and must pay attention to all those practices that distance us too much from it and/or prevent us from reaching and understanding it.
Personally, I think that doing "technique first," then "note reading," then "interpretation" makes us reach the goal with difficulty, rarely, and sometimes not at all.
Everything is already inside the piece and we must reach, as much as possible, the "whole." It is not certain that we can reach it by diligently lining up all the aspects of the whole... but separately.
Years ago I held a different opinion: I would have thought of this as "sloppy makeshiftism."
Now I think that truly letting Music suggest the technical solutions, i.e., the "how to do it," and not losing sight of the Author's "ideas" is of great help.
It is clear that for a short time we can "distance ourselves" to experiment and understand in detail, outside the context of the piece, things that remain more "difficult" for us... but not for long. In the long run, it would be like glimpsing the path without ever being able to see the destination.
I think we must remember that we are making Music and that Music contains everything.
I am personally opposed to remaining for a long time in a distant world made of "slow study tempos" and contrasting rhythmic formulas that distort the required accentuation to be assimilated. I believe this path does nothing but prepare us for what "we must not perform" and that it does not work at all as an anti-whole or antibiotic against the "vices" or "errors" committed.
It is therefore advisable, even before studying the piece, to research, listen, understand... and even try some easier passages to enter into the "character" of the piece.
Now, yes, a slow, fragmented, "attentive" reading is fine, but always taking into consideration the final tempo speed, as well as the quality of sound, touch, the phrasing, etc.
I have seen students, and not only, study two pages of a Beethoven sonata, note by note, slowly, for two years. Perhaps with the aspiration to perform it, and only then, perfectly at the right tempo.
The fact is that, often, at the right tempo, with "interpretation"... which will come later... everything changes. The gestures and bodily participation are different and could require, for example, a different fingering, which instead worked very well, or almost, slowly! That is to say.... by approaching the "whole," we might realize that the exhausting and extremely long study of individual parts in a world far removed from performance has perhaps served little or, at least, has wasted much time in our study.
I would like to stop here for now, leaving it to others to develop the theme.
I return to remember what was thrown onto the table: "but so, do we have to interpret immediately, tomorrow, the day after tomorrow, or in two years??" Who knows!!!!!! 😆