I think that would have helped me the other day. I needed to debug a PWA on safari and i don't own any apple products. So i downloaded a windows VM machine and installed safari on it. It worked out but it was a pain.
You can get much more recent Safari (and iOS simulator Safari) releases through macOS virtualization, https://github.com/sickcodes/Docker-OSX though this skirts some Apple EULAs. If you want desktop Webkit rendering and JS interpreter parity, https://webkit.org/downloads/ also offers several Linux webkit browser options that would also likely be more accurate than Safari v5.
But all of you are right. The safari version that i tested don't even support arrow functions.
>Safari 5.1.7 for Windows, released in 2010 and now outdated, was the last version made for Windows. https://support.apple.com/en-us/102665