It has happened at least once before, and it seems to be happening again. Samsung has gone ahead and released the security patch for the upcoming month for one of its devices, before Google has released official details of what that patch entails or rolled it out for its Pixel phones. The device in question is the Galaxy J3 (2017), which is receiving an update in the Netherlands and Luxembourg with the April 2018 security patch.
Naturally, there’s no telling what or how many vulnerabilities the April patch will fix, though it won’t be long before Google makes the customary announcement on its website.
https://www.sammobile.com/news/samsung-already-pushing-out-the-april-2018-security-patch-to-one-device/