Very odd: I remember my 2013 SL working the way you are asking for: it would pair to the phone in the car. If my wife took the car (and I wasn't there) it would pair to her Android. When I drove it to work the next morning, it would automatically pair to my Android. In fact, when we were both in the car at the same time, it would pair to the first phone in the list (which originally was hers, but I later swapped them to make it prefer mine).
LEAF '13 SL+Prem (mfg 12/13, leased 4/14, bought 5/17, sold 11/18, 34K mi, AHr 58, SOH 87%)
Tesla S 75D (3/17, 45K mi)
Tesla X 100D (12/18, 23K mi)
ICE free since '18
100K+ 100% BEV miles since '14