Many years ago - a different vehicle I had been researching was manufactured with "deep tint" by default (more than adequate, as five years of having it proved). Yet, the dealer wrote in extra tint from the get go, I had to request to delete it.
Fast forward - same here.

Hence, the question - what are the specs for the tint that Defenders come out from the factory with?

The exact answer might turn out quite interesting; one of my other cars (different brand) "build list by VIN" contains an "oversized AC upgrade" that I didn't request, nor it was present in any configurators or dealer information resources, nor it was present in configurations for this exact model elsewhere in US, it seems to be a regional feature that they just threw in at no charge (and that was a good thing, even with this feature the car is barely keeping up, given the fact that the summer temperature went quite a bit up since I got it).

Is JLR known for doing this kind of thing?

 

Privacy glass is typically 20 neighborhood on SUVs. I got my fronts tinted to 30 and they are lighter than the factory tint on the rear Defender windows. But not a ton lighter, so my guess is around 20. Limo tint is 15 as another reference point.

 

20 on the front two windows matched the rest of the vehicle, so I'd say it's 20ish.

 

I just had mine tinted last week. I had 30% put all on front driver and passenger windows, 55% put in the rear to darken it a little more an add ceramic coating in the tint to help with heat reduction, and 70% on the windshield.