Are there any mapping guidelines (OSM wiki?) stating that it was not a valid way to map landuse with multipolygons? Or is it just your personal view on uselessness of certain map features or mapping techniques?

While you correctly admit that it may be easier to use multipolygons to map landuse, it also reduces maintenance and further editing/refinement effort, especially in densely built-up areas. How can you know in advance if I plan to maintain the landuse in question long-term or 'just move a few nodes around'?
