Not necessarily, according to the description there are various ways to make it work.
WITHOUT GATEWAY:
Products can be controlled via an Amazon Echo Plus without a gateway or additional station. The Echo Plus can be set up via the free app.
WITH GATEWAY:
Can be controlled via Amazon Echo, Echo Dot or Echo Show in combination with a partner gateway, Google Home in combination with a partner gateway via voice control. Without voice control, a partner gateway is sufficient. The gateway is set up via the appropriate app. Compatible partner gateways are e.g. Magenta SmartHome, SmartThings or Schwaiger4You.
Alternatively, Smart+ products can be controlled manually via a corresponding remote control.