This reminds me of KEY JOIN in Sybase which, unlike this syntax, does not require to specify the foreign key. I find Sybase's syntax to be too implicit, and challenging to port to other dialects; JOIN FOREIGN with explicit PK reference looks much better.
I wonder how it is expected to work with non-table references (views, CTEs, subqueries), especially when the columns involved in the foreign key (on either side) are not returned explicitly by the referenced object.