A single rest should not span a primary beat boundary beyond the standard consolidation table

Rests are held to a looser standard than notes (no sustain to obscure), but a rest still should not silently swallow a beat boundary: within a beat, rest values consolidate upward to the largest legal symbol, but a rest should not cross into the next beat unless it fills that beat and the next completely as a recognized whole/half/dotted value for full-beat or full-bar silence.

A half rest placed starting on the 'and' of beat 1 in 4/4 (onset 0.5, duration 2 beats, ending at 2.5) — it neither starts nor ends on a beat, straddling beat 2 invisibly.

Gould, Behind Bars, ch. 'Rests', the beat-boundary rest table; Read, Music Notation, ch. on rests, the same 'rests may combine within but not straddle a beat except as whole multiples' principle.

This rule can be decided from pitches, durations and voices — no layout required. A validator can check it before anything is drawn.