The "designed for a specific tire" in street applications is typically because of very high performance (speed) considerations.
Most passenger cars aren't capable of the Bugatti Chiron Super Sport's theoretical 304 mph (it's got a governor for 273mph) and that car can't achieve that speed with a set of all season radials which would shred getting there.
Even for this car, the manufacturer went from a specific tire design in the Veyron at $30,000 - $42,000 per set to standard mounting, but then chances are you would have to special order the 285/30 R 20 (F) 355/25 R 21 (R) rubber as most service stations won't have them on hand.
It's not that Subaru manufactures a car for a specific tire, it's that some tire manufacturers produce tires appropriate for a Subaru.
A Forester, like most other passenger cars, needs tires that have an appropriate size, weight rating and design for its intended use to work well, which in the case of a Forester can vary by driver.
Commuter and off-road drivers won't want the same tires.
Performance in hot dry states and cold wet ones won't be optimized if they used the same rubber.
The Chiron on the other hand is made to go fast on pavement, period.