[1] 336/16

[2] Although it is possible to eat the fruit without removing it, as one can take a bite from it while it is attached, nevertheless being that this is also forbidden, as there is no greater form of removal than this, therefore the decree is intact. Now although biting off a fruit attached to a tree is not a regular way of removing a fruit, as regularly a fruit is removed with one’s hands and not his mouth, and hence one is Biblically exempt for doing so, nevertheless it is Rabbinically forbidden, as is nursing from an animal. [ibid] Regarding why this is not considered a decree upon a decree, this is because the main worry is that one may come to remove it with his hands, which is the normal way of removal, as he will forget that it is Shabbos. It is only Derech Agav that it is brought that eating while attached is forbidden. [Ketzos Hashulchan 142 footnote 1 in answer of the question of the Iglei Tal. Vetzaruch Iyun as the simple implication from Admur is that if not for the Rabbinical prohibition we would not suspect for the person removing it with his hands. Hence perhaps the explanation is as follows: The normal suspicion is one may come to remove it with his hands, however on this someone can ask, why would the Sages decree against a matter if there is a permitted way of accomplishing his request, such as here by eating it while attached. Hence Admur explains that this too is forbidden at least Rabinically, and since there is thus no permitted way of accomplishing the eating of the fruit the Sages applies their decree.]

[3] As the entire benefit of these items are their smell which one can benefit from while they are still attached. Hence there is no reason for one to need to remove it. [ibid]