Revs dropping when steering wheel turned when idling

My early 2000 S-type 3.0 Automatic idles fine but I’ve noticed when turning the steering wheel when in Park and idling the revs drop down as the steering wheel is turned - is this normal? I’ve never come across this with any other cars.

When I first start the car, the revs are at over 1000rpm for a while then it drops down to below 1000rpm and idles fine until I turn the steering wheel.

Greatly appreciate any advice

That is normal for all cars, especially if you go to full lock. If the engine keeps idling it can take the load and so it’s fine. A higher cold idle shows the idle valve seems to work.