R. Eliyahu Mizrachi and Maharsha both write that that the term "ein___ela___" (x is only y) doesn't mean that is the only thing that it means, but rather that this is how it is being interpreted there.
R. Mizrachi in his commentary to Rashi on Lech L'cha (15: 3):
אין הבט אלא מלמעלה למטה...ואינו רוצה לומר שכל הבטה היא מלמעלה למטה...אלא הכי פירושא אין הבט האמור פה אלא מלמעלה למטה, דומיא ד"אין עמידה אלא תפילה" ו"אין פגיעה אלא תפילה" וכו
See also Mizrachi to Vayera (22: 2).
Maharsha writes in Chiddushei Aggadot to B'rachot (26b):
אין שיחה אלא תפילה וכו' רצה לומר במקום הזה אינו אלא תפלה כמש"כ הרא"ם
Rabbi Saul Lieberman writes the expression can have to meanings; a strict interpretation of a word in context, or a Midrashic interpretation.
It appears that comments formulated אין ... אלא which are incorporated in the Halakhic Midrashim have their origin in a very ancient commentary of the Law. Most of these comments undoubtedly provide the plain meaning of the text. In course of time this vigorous assertion (i.e., it is nothing but . . .) was extended even to Midrashic exposition, but as such it was almost exclusively limited to the narrative parts of the Bible. The use of this emphatic formula for a Midrashic comment therefore becomes one of the characteristic exaggerations of the Aggada; it degenerates into a mere literary phrase, and the Rabbis themselves will not take a comment introduced by these words more seriously than any other Midrashic interpretation in the Aggada.
See also this post on the Parshablog which argues that "ein__ela___blank" is often used as a poetic overstatement.
 Hellenism in Jewish Palestine (1962). Page 51.