How are you going to design database schemas if you don't know Postgres? Controllers and models if you don't know Rails? Components if you don't know React? I don't think design and usage are such separate skillsets.
Put another way, wouldn't you want the Postgres expert to design your Postgres schemas? Or the Rails expert to lay out your Rails application?
Again, I agree on that, my perception of architect is that it's a strongest software developer with a high specialty in designing systems.
It shouldn't be a person out of the software loop, it wouldn't make sense.
I never intended to create a low bar for the title, nor a separate role from "software developer". I'd expect the architect to still be a software developer able to contribute to the existing stack.
Put another way, wouldn't you want the Postgres expert to design your Postgres schemas? Or the Rails expert to lay out your Rails application?