Dust-disc cavity sizes that could be produced by the detected companions. For each source with a significant proper motion anomaly, blue distributions show the cavity sizes each Sect. 3.1 (Fig. A.2) companion could produce in their discs (from bootstrapping uncertainties). These distributions consider the mass ratio of each source and the theoretical prescription presented in Ragusa et al. (2025). Uncertainties in stellar mass, companion mass, and semi-major axis have been propagated consistently. We consider all possible companion inclinations and eccentricities. Vertical red lines show the observed dust cavity sizes at millimetre wavelengths (Fig. 1, with a generic 20% uncertainty).