Zed had already targeted macOS when 10.15 still had over a year of support left https://github.com/zed-industries/zed/commit/b400449a58507cc... and some variant of x86-64 macOS will still be supported through 2028. Neither of these were adding support for really old things, one is current for many years to come and just there hasn't been a reason to break 10.15 support yet so why bother.

Meanwhile Windows 7 is already over 2 years past the end of extra-extended support at the time this new code was written with Windows 7 support still in mind. Which is nice, but a very different scenario.