??? ... A380 FCOM (my bolding)
Little, if any, power above idle thrust can be necessary to move the aircraft (e.g. approximately up t0 10 % THR at heavy weight, with a uphill taxi slope). Excessive thrust application on engines can result in exhaust-blast damage (e.g. on airport signs). The Flight Crew should use symmetrical thrust. When the aircraft begins to move, less thrust is necessary.
If the inner engines are located over unconsolidated or unprepared ground during taxi, avoid high thrust settings on the inner engines (i.e. engine ingestion (FOD) risk increases). If additional thrust is necessary, the Flight Crew should preferably use the outer engines.
Outer engines less susceptible to FOD, so I guess they don't want the airport signs blown away.