Google is opening the doors to something that ultimately should make the Google Assistant much more useful: now it will allow other companies to create custom commands when the Wizard is integrated into their products. Therefore, the manufacturer of a smart dishwasher that supports the Google voice assistant could add a command to "start a hypercycle", although that is not a universal feature found in other dishwashers.
At this time, devices with Integrated Wizard are limited to a series of universal commands that Google has set itself, such as "on", "off" and "dimmed". Additional functionality can be added through Actions (applications, basically), but that requires an additional step for owners every time they want to use it. That is obviously quite limiting if you are trying to build a more advanced product. Google seems to expect that by delivering part of that work to the manufacturers, it will give them much more flexibility and make the Wizard more useful at the same time.
Manufacturers can choose the amount of commands to build
Google suggests, for example, that a kiln manufacturer could use this capability to program voice controls for specific configurations, such as "setting the oven for convection and preheating to 350 degrees." On the one hand, Google could probably universalize that and have all ovens use the same commands. But, on the other hand, a manufacturer that takes seriously the task of making the Wizard useful could go much further if desired, allowing even more voice control than standard Google commands would cover.
LG already seems to be taking advantage of this. Before today, you must invoke an Action saying "talk to LG" before issuing a command, but now you can only say what you want the LG connected device to do. That is a much faster and more natural interaction.
What may be more interesting are the most extravagant devices that this will enable. Google has created a robotic arm that classifies socks and responds to voice commands to illustrate how serious it is to let the Wizard do anything with a developer's codes.
In addition to opening the Custom Commands Wizard, Google is also announcing a couple of other new features today: now you can have specific assistant actions that send you notifications on your phone. The actions also improve the media playback capabilities.