At first the gemara thinks that consuming the juice of fruits of orla is not a normal way to eat the fruit and therefore qualifies as שלא כדרך הנאתו. The gemara concludes that the rationale to permit fruit juice of orla is permitted because we regard the juice as being זיעה בעלמא - sweat of the fruit without the real taste and therefore isn't considered to be eating the fruit of orla.
Tosafos asks a fundamental question. We pasken that טעם כעיקר is d'oraysa (unlike Rashi in chulin). How could the fruit juice be any less significant than ta'am ki'ikar? Tosafos leaves the question unanswered.
The gemara says in Brachos that one makes a shehakol on fruit juice because it isn't considered the fruit, rather just זיעה בעלמא just as the gemara says in the context of orlah. However, in Brachos 39a the gemara says that on vegetable soup (beat soup) one would make a בורא פרי האדמה. Tosafos writes that there is a difference without articulating the difference. The Rosh (18) explains that the vegetable soup has the taste of the vegetable and therefore deserves the same bracha as the vegetable. But the juice of a fruit doesn't have the taste of the fruit. The Rosh then adds - ואפשר שאם בישל הפרי ונכנס טעם הפירות במים מברך עליהן בורא פרי העץ. The Rosh seems to understand that the cooked juice of the fruit contains the full flavor of the fruit, whereas squeezing out the cold juice doesn't capture the full flavor.
The Rashash indicates that this is also the rationale for why we don't forbid the juice of orlah fruits based on ta'am k'ikar. Although if one would cook the fruit, the full taste of the fruit would come into the water therefore it would be included in the issur orlah, but without cooking the fruit we would not give the juice a status of the fruit based on ta'am k'ikar.
It seems that the ואפשר of the Rosh, implying that he isn't entirely convinced, is entertaining the possibility of the distinction between fruits and vegetables. Perhaps only by vegetable soup would we say that one makes a borei pri ha'adama, but a fruit soup would be she'hako, not ha'eitz. However, the Rosh leans toward the approach of not distinguishing between fruits and vegetables. Therefore, any water in which the fruit or vegetable was cooked in would obtain the bracha status of the fruit or vegetable.
The Rashba (cited in divrei chamudos) considers the distinction to be whatever is normal and regular to be eaten that way. Fruits are eaten by eating the fruit, not squeezing the juice and not making a soup, therefore if one would either squeeze out the juice or cook a soup with it, the bracha would be she'hakol. But, vegetables which are routinely cooked and turned into a soup, the bracha would be ha'adama. Based on this approach, there is no difference between cooked soup and squeezing a fruit, either way the taste may be significant, but since its not a normal way to eat the fruit the bracha would be she'hakol. According to this approach, it remains difficult to understand why fruit juice of orlah would not be אסור מדאורייתא based on the concept of טעם כעיקר.