hi
it is not an old wives tail !

look at your dip stick it will say to check fluid level at idle warm in N not park for correct tranny fill level !
fluid does not get sent to convertor in park so when it is cold and you first put it in d it has to fill convertor before building psi to engauge clutches to drive the car , !
place it in N after a cold start for app 20 sec fills the convertor and then placing it in drive should be able to drive normal .