  Jammed soft matter systems are often modelled as dense packings of
overlapping soft spheres, thus ignoring particle deformation. For 2D (and 3D)
soft disks packings, close to the critical packing fraction $\varphi_c$, this
results in an increase of the average contact number $Z$ with a square root in
$\varphi-\varphi_c$. Using the program PLAT, we find that in the case of
idealised two-dimensional foams, close to the wet limit, $Z$ increases linearly
with $\varphi-\varphi_c$, where $\varphi$ is the gas fraction. This result is
consistent with the different distributions of separations for soft disks and
foams at the critical packing fraction. Thus, 2D foams close to the wet limit
are not well described as random packings of soft disks, since bubbles in a
foam are deformable and adjust their shape. This is not captured by overlapping
circular disks.
