Yes the spare is from my R1T. Its the same wheel and tire from an R1S but I don't believe it fits in the area under the floor. I think ppl are just placing it in the area cargo areas for road trips.
Brand new Rivian A/T matching spare tire and wheel along with the service kit. $1235 plus tax from the Rivian Gear Shop,
$1000 picked up in Mission Viejo.