Don't fall for it.  They are practically worthless and pure profit for the dealer.  Unless you have your attorney go over it to see exactly what is covered and what is not, the dealer will always find a way to tell you "that's normal" or "that's not covered."

It's an insurance policy, and has a deductible. It's not worth it.

In my experience, my girlfriend bought one for her 2017 Mustang, before i knew her, and the purge valve was replaced under the "warranty". They still charged her $150 with a "covered" service. I replaced the same part in my 2017 with an OEM part in ten minutes, using a $100 scan tool. The part cost $50. 

Usually "warranty extensions" are worthless.

A lot of these "warranty extensions", are written like insurance policies (and that's usually what they basically are). From my experience, if it's inexpensive, and the policy is both long and overly complex - it's probably worthless.

Read the fine print, and make sure you understand what they're trying to sell you. If the text requires someone who's both a mechanic and a lawyer to understand - I'd avoid it. If it's written in a clear fashion and has a clear list of what it covers (usually not much, things like "transmission internals") and for how many miles (Where I live I've seen things like "4 years or 12,500 miles! which ever comes first, and these are useless), and if the coverage is good and long (almost never the case), maybe that's an option.

Also, although it's sold by the Subaru dealer - most of the time this warranty service has nothing to do with the dealer/manufacturer. Check who actually does the repairs / diagnosis, a lot of the time they can offer the same service (with the same policy/terms and conditions) at a lower price because then they aren't paying Subaru to use their marquee and dealers to advertise the service.

BUT I wouldn't count on it too much. Reminds me of how a member of the forum was denied warranty service by Honda, while he still was covered under powertrain warranty - apparently Honda claims that fuel injectors aren't part of your powertrain (just an example as to how the fine print changes everything - basically, as I see it, that "powertrain warranty" only covers the cylinder block). 

You might get lucky like Doug DeMuro on YouTube, he had purchased a Range Rover and added bumper to bumper warranty for $3,899 and the total payout he has got is $21,276. That's a really rare case where the warranty was coverage was good and the service provider is honest, again - it all depends on the fine print. 

Personally, I had a bumper-to-bumper "warranty extension" but it had a deductible - the only time the car had issues during that period it ended up costing less than the deductible. But a friend of mine had a Dry-DSG mechatronic failure and they've done the $2,500 repair no questions asked.

But on a Subaru? I doubt it'll breakdown in a manner covered by the "warranty" that'll cost over the $1,000+deductible any time soon.

Also, the last time I checked out a Subaru I didn't find much tech in it - things like a touch infotainment screen, power operated sunroof, and collision avoidance are kind of basic for the Subaru's price level. I wouldn't say it's packed with tech, I'd worry more about getting insurance on the transmission as these are the weak-spot in modern Subarus.