Currently it is not possible to apply the Solid fill option on Offset Cross-sections (only available for planar cross-sections).
It would great if this option was also available for offset sections.
An example of where this would be useful is in the case where a Full(unfold) cross sectional view in a drawing is used to clearly layout the internal workings of a complex design, like a gearbox/transmission.
Here you could fill each component being sectioned with a different colour, creating a clear and useful view of the design internals.
For a workaround one could of course apply hatching with really small spacing, but this drastically affects performance, especially on larger more complex models.