I think it is rather Preview app bug and Apple fault.

Here is how @Anonymous PDF looks like when printing from Preview app:

The same FPF printed from Adobe Acrobat DC with default settings:

@Anonymous , you can instruct your clients to use Adobe Reader instead of Preview app for printing. I think it will not be difficult for them.

Meanwhile you can leave your feedback here:

https://www.apple.com/feedback/macos.html