Is there any harm in caulking the bottom of this electrical conduit plate or should it be left unsealed?
Yes, the gap is improper, and the conduit is not anchored,
Further it may need  to be a different type of conduit if it is subject to physical damage at that location (it didn't pull itself out). For instance, replacing the sharp elbow with a LB conduit body for schedule 80 PVC would be a step in the right direction.
The white cable we can see in the conduit is NM-B type, which is not allowed outside, underground or in wet locations, even if it is in conduit.
Even if it was allowed, it is too large for that size of conduit.  The conduit ID must be 138% of the widest dimension of the cable (which means UF cable won't work here either).
The right thing for running in conduit is THWN individual wires (i.e. loose wires, no sheath. Don't need a sheath in conduit.