The rendered-page inspection now looks at both sides of your breakpoints. It used to permute viewport height and scroll position and nothing else, so a complete capture set could sit entirely on one side of every breakpoint a surface has — exercising each layout rule only where it already applies. A channel is a band of viewport widths, and a set is complete only when it covers every one your surface has.
Tell it your breakpoints and it captures either side of each. Declare them and the bands they bound become the required channels, captured at the widths that straddle each boundary — declare 1152 and you get 1151 and 1152. Declare none and two bands apply, narrow at ≤480 and wide at ≥1024, and the run records that it fell back. Those two leave 481–1023 uncaptured, which is where a great many real breakpoints sit; declaring yours is what closes it.
The floor rises from four captures per route to eight. Four heights-and- scroll-positions in each required channel, and four times *n + 1* where you declare *n* breakpoints. An existing capture set becomes incomplete at this version, which is the intended signal.
A capture's width now means something to the reviewer.frontend-reviewer is told to use it: it decides which breakpoint-scoped rules a capture exercised at all, so a failure absent from one channel is no evidence it is absent from another.