WZ Sge-type stars are an extreme subclass of dwarf novae characterised by very rare, large-amplitude superoutbursts. Within
the disc instability model (DIM), such events are explained as being triggered by enhanced mass transfer from the donor star.
We present an analysis of observations of a sample of WZ Sge-type systems in deep quiescence to assess the consistency of DIM
predictions with their observed properties. We find that accretion discs in quiescent WZ Sge-type systems have very low
mass-accretion rates of a few $\times 10^{-13}$ M$_\odot$ yr$^{-1}$. The discs are entirely optically thin, and their physical conditions
-- such as surface density and effective temperature -- remain well below the DIM thresholds required to trigger an outburst.
Observationally, no increase in disc brightness is detected prior to the superoutburst, indicating the absence of a transition
to an optically thick state, in contrast to DIM predictions of a gradual disc thickening preceding the instability. We therefore
find no observational evidence that superoutbursts in WZ Sge-type systems are triggered by enhanced mass transfer from the donor.
Furthermore, the inferred mass-transfer rates in these objects ($\dot{M}_{\rm tr}$$\sim$5$\times 10^{-12}$ M$_\odot$ yr$^{-1}$) are at least
an order of magnitude lower than commonly assumed. We argue that the widely adopted value of $\dot{M}_{\rm tr}$ for the prototype
object WZ~Sge is likely overestimated. Finally, we show that in quiescence the accretion disc radius in all systems is close to the
tidal truncation radius and exceeds the 3:1 resonance radius, confirming earlier results and calling into question the standard
interpretation of superhump formation.