Week one of driving my new (to me) '89 GL Camper with a 2.1 Wasser...

I noticed for the first time at the DMV of all places, that with the engine
shut down, and the automatic selector in the D (Drive) position-- my wheels
are free spinning (i.e.: I rolled down hill with little or no resistance).
I checked the other positions as well-- and with the exception of P (park)--
I free wheel (or at least feel like it).

As my Bentley has yet to arrive-- is this by design? or do I have a problem?
Every automatic I've ever driven would indicate that something is amiss.....