The "Search" screen refreshes "on ENTER": from a pure UX perspective (in a world with super computing power) this would not be necessary, but for performance reasons it must be as response time is critical to UX, in doubt trumps other UX factors. So as it anyhow operates differently than searching in the "Installed" screen (instant filtering, no need for ENTER), thus already no consistency anyhow, I don't see the problem.
In the "Installed" screen the user starts typing and immediately gets visual feedback (the list elements change, with a high probability already after typing the first character). Thus the user very unlikely triggers enter for submitting a search ("I already got a result, so why would I ask for it again?").
In the "Search screen" the user types a query, and nothing happens. Already after the first or second character type it's clear that this alone is not enough. According to universal key binding convention, the user presses ENTER. Now what could happen to a user being used to the behavior "ENTER launches app" from the "Installed" screen, is that the user browses within the results (with the Dpad) and wants to launch it with ENTER. Currently nothing (seemingly) happens (query is unchanged, package-list unchanged, thus no retriggering), as there are actually two focuses in this screen. The typing focus is still in the search field ("remains hot", no need to TAB between search field and search result area, or moving with the dpad from the topmost result into the search field, as often found on Desktop apps) With an unchanged query, ENTER could simply launch. With a changed query line of course, ENTER must trigger the query.