Right. You are a power user and for you it's fairly simple. Think of all the casual users that can copy and paste a few lines of code (i.e. The Virtual Switch to Motion by @ogiewon that I posted) and know how to make an Alexa Routine. With this, they don't have to run other computers in their homes and don't have to learn any different setups or systems they don't really want to.
Many have been asking for the ability to control the inexpensive Alexa enabled WiFi devices they own or are thinking of buying, but without Google compatibility and a lot of extra parts and setup. This was previously not possible, and now it is. Yeah, most of those WiFi devices are still cloud based garbage and I don't personally recommend them for numerous reasons, but to at least have the option to make bad choices is nice
What's better about this than a driver for many of the junk WiFi devices is, this won't affect the hub performance at all. But it's not just inexpensive WiFi only devices, it's the expensive ones too. Right now I'm controlling my Delta VoiceIQ faucet with Google Assistant Relay, but if this isn't a burden for me (such as pausing my music like @stephen_nutt pointed out), then I may just switch it to Alexa custom commands instead of the current method where I have to create an Alexa Routine, to trigger a virtual switch that then sends the command via GAR. That's a real pain to setup new custom routines when I want a custom water volume request. This would dramatically simplify that.