To a first approximation, that's what it still is all these years later. The software might be called iPadOS now but it's not fooling anyone that it's much different to iOS.
When I release my apps, I only do so as iOS, and that runs on iPadOS.
In the code, I check for the environment, in some cases, and do things differently, if it's an iPad.
But lots of apps can just treat it as a big phone.