At least one improvement has been made to the spec over the years: the iPhone X / iPhone 8 introduced support for fast charging through the USB-PD standard which meant something had to be upgraded. I’m fairly sure that change did not result in physical changes to the connector though. It has always remained backwards-compatible.
Did they did improvements on it or it has been always the same identically connector?
At least one improvement has been made to the spec over the years: the iPhone X / iPhone 8 introduced support for fast charging through the USB-PD standard which meant something had to be upgraded. I’m fairly sure that change did not result in physical changes to the connector though. It has always remained backwards-compatible.
One of the iPad Pros supported USB 3 speeds over lightning, before they transitioned the iPads to USB C. https://www.zdnet.com/article/ipad-pro-lighting-port-works-with-usb-3-0-but-theres-a-catch/