In France, many military and nuclear facilities are also smoothed out in google maps. It seems a bit ridiculous since you can easily see public (free and paid) satellite images of the same places.
If you look at the historical imagery in Google Earth, it'll show your the 2015 imagery fine: https://i.imgur.com/Jk8Kn1r.png
It's noticeably lower resolution than the surrounding 2017 imagery, but it doesn't appear to be censored in the same way (it's of the same quality as the surrounding areas when imaged in 2015).
It does the same for what appears to be a large circular antenna installation just to the west of here.
Edit sorry I can't link to satellite view from mobile. It's the Mola Fortress on Menorca.