No correct information here.

SPOT most definitely does not use Iridium, SPOT uses Glovalstar satellites, and is owned by Globalstar, having been developed by them and deployed in part to make use of their L-band simplex data capabilities in their satelites while their S-Band voice capabilities were failing with technical problems.

inReach uses Iridium, a competitor to Glovalstar, and which offers a significantly technically superior network to the Glovalstar L-band capability. Starting with it being duplex, which is why InReach can do two way messaging, and why the data transmissions are fundamentally more reliable.