shome'a k'oneh as a hefsek

Are we to take shome’a k’oneh literally – listening is a form of talking, or does it simply mean that listening itself suffices to fulfill mitzvos without the need for actual speech? In other words, is shome’a k’oneh actually a form of dibbur, or a substitute for it? This question is usually presented as the point of disagreement between Rashi and Tosfos (Sukkah 38, Brachos 21) in the case of someone in the middle of shomeh esrei who hears kaddish or kedusha. According to Rashi, the person should stop davening and listen, fulfilling the obligation to answer through shome’a k’oneh. Tosfos disagrees and holds that pausing to listen would be a hefsek. If shome’a k’oneh is taken literally as a form of dibbur, we understand Tos.’ position that it would be no less a hefesk than actual speech, but if shome'a k'oneh is an alternate to actual speech, Rashi’s position seems to make more sense.

A third approach to this case is given by the Ritv”a, who applies the rule of ‘kol hara’uy l’bilah bilah m’akeves bo’. Even where speech is not required, the potential to be able to speak is. I can call on shome’a k’oneh to fulfill my obligation to recite hallel because at least theoretically I could read it myself. I cannot call on shome’a k’oneh in the middle of shmoneh esrei where I cannot stop to speak.

This is some of the classical stuff on the topic, but my brain is still stuck on the kriyas hatorah question in the previous post…