It really looks like it uses the normal way to download extensions; the Web Store.
I'd be more concerned that the only thing the patch seems to do is not activate the hotword extension. It seems to still download and install it. I mean, maybe I'm wrong here. I think that checking through https://chromium.googlesource.com/chromium/src/+/f269d3b5482... for ENABLE_HOTWORDING is the right thing to do if one wants to understand the change that was made.
I'd be more concerned that the only thing the patch seems to do is not activate the hotword extension. It seems to still download and install it. I mean, maybe I'm wrong here. I think that checking through https://chromium.googlesource.com/chromium/src/+/f269d3b5482... for ENABLE_HOTWORDING is the right thing to do if one wants to understand the change that was made.