I could not find anyone addressing this. I guess the issues are obvious? I am not satisfied with my understanding of the sugya, but here is what I understand:
The basic example of bishul for the mishkan is boiling the dyes, so the basic definition of cooking would include cooking something in order to extract its properties.
Shabbos 106a: "All destructive actions are exempt, except for injuries and fires". Rashi explains that according R' Shimon, who requires a maleches machsheves, and says mlacha sh'ein tzricha lgufa is patur, injuries and lighting fires would never meet this standard, and therefore in these two cases there is no standard of tzricha lgufa. (see also Rashba).
If I understand correctly, R' Yehuda argues based on the dye preparations that melachos only need to be constructive, but they do not need to be ltzorech gufom. "ma li bishul psila, ma li bishul samimanim". Boiling dye is by its nature not tzricha lgufa, which means that melachos do not have to have this requirement. The gemara does not give R' Shimon's counter-argument, and I did not see any Rishonim discussing it, but he must hold that preparing the dyes was ltzorech gufo. It is possible that that R' Shimon has a somewhat wider definition of mlacha shetzricha lgufa, and that it includes any mlacha whose direct result is constructive and desired. (See Ramban for a similar discussion). Basically, R' Yehuda would have a very strict definition of tzricha lgufa, and then prove from bioling dyes that tzricha lgufa is not necessary, while R' Shimon has a looser definition of tzricha lgufa, which includes boiling dyes. (It does not however include destructive actions except in cases of injury and fire-related activity. Again, see the Ramban.)
If this is correct, then making tea would be a mlacha shetzricha lgufa according to R' Shimon, because any cooking with a constructive intent is tzricha lgufa, and the definition of the melacha as "effecting a change in an object through (fire-based) heat" is technically incorrect.
This mostly relies on the Ramban's assertion that tzricha lgufa means only a direct constructive effect, but the other Rishonim to not seem to agree, and they define tzricha lgufa as when the person desires the direct effect of the mlacha, in accordance with its primary definition. If cooking is defined as
"effecting a change in an object through (fire-based) heat", then we are back to the question why R' Shimon does not conclude from the case of dye preparation that we do not need tzricha lgufa. Possibly, (no source for this) R' Shimon would say that affecting the water is no different than affecting the material you are boiling, and that cooking would be defined as using heat to effect a change in an elemtns properties, without refering specifically to the properties of the material which is being boiled. Again, tea would be a mlacha shetzricha lgufa with this definition, exactly like boiling dyes.
Another possibility is that tea is included in the rule of "kol hamekalkilin peturin chutz mchovel umaavir." If we ignore the question of dyes and the definition of cooking, and accept our initial understanding that tea is a melacha she'in tzricha lgufa, the questio is if cooking requires a mlacha shetzricha lgufa. The gemara says that R' Yehuda holds the case of maavir is not mikalkel, because there is no difference between boiling dyes and melting lead. In other words, maavir is referring to boiling, not only to burning wood. I am not sure about this, but from what I can tell most of the Rishonim understand maavir like this, that it is referring to all usages of fire.
To conclude, tea is not mlcacha sheintzricha lgufa either because tzricha lgufa means a direct, constructive outcome, or because the definition of cooking includes improving the water by extracting the properties of the tea, or because cooking does not require tzricha lgufa.
