That makes sense, that iPad had 5 years of major OS updates (2013-2018), which included the browser, but Apple provides security updates and critical bug fixes for at least 2 years after major updates end. That model stopped at iOS 12, first released in 2018, which received security updates for an especially long time, 2023.

In that era, Safari added new features, including adding support for web standards, in the major update and in a .1 update about 6 months later, Safari 12.1 came out in March 2019.