I think we each live in our own bubbles. I see very few people on macs or linuxes, almost everyone uses Windows and they're fine with web development. What's so unixy about node/npm? They feel like very good windows citizens.
Obviously this isn't a deal breaker in most situations, but it is a bit annoying. I've observed similar performance problems running Webpack on Windows in the past.
Also take a look at this talk on NTFS, file system speed, and how the presenter optimized the Rust installer: https://youtu.be/qbKGw8MQ0i8 . There is an awful lot that can be done to tools that deal with lots of files to perform well under Windows too.
No. It was the VFS design. They have lots hooks and extension points for 3rd party, there is no way to improve without breaking backward compatibility. It was the reason why many antivirus was broken in the first few releases of windows 10.
The only time I see Windows frontend devs is full-stack .NET shops or low cost outsourcing centers. If nothing else then just for practicality - you need to test on Safari and iOS so might as well get Mac devices.