If the developer were to have made a swift version for Mac, a C# version for Windows and a C++ version for Linux, that would be very bad. A startup simply cannot reliably keep all up to date, and the product would suffer.
If they wrote it in Java and in that way claim multiple platforms, I daresay it would be even worse, on all platforms.
If they used a tool that did the conversion for them, it would likely be a security and usability disaster, even though I need sources for that.
So a bias against a multi-platform tool is understandable.
The one exception is a Javascript tool, since things like Chromium have a LOT of effort put into them by companies with thousands of developers on payroll. However the number of tools that should run in such a environment is limitted.