I'm typing this on FreeBSD. If the most interesting part of a Mac to you is the BSD layer ... Well, I doubt that. People like Mac for the UI and Cocoa stuff, plus hardware and integration thereof.
The way you've substituted "BSD" for macOS really doesn't make sense. Yes, there is BSD code in MacOS, quite a bit of it in fact. But they're not the same thing.
You are right that people that buy a Mac don’t get it for the FreeBSD kernel. However, most people that complain about not being able to run Linux on a M1 can be just as productive with the alternatives on macOS.
For 99% of other things that run in a terminal, you can get it to work in FreeBSD/macOS. Also, for Python folks, there is anaconda distribution that is agnostic to the underlying OS. Ditto for node or ruby development. Also Gui Emacs and vi have decent ports to macOS.
That said, I guess if you are doing some custom server side development that really needs Linux, you will have a hard time with M1 - virtualization and emulation don’t mix and your code might not be portable enough.
Again as a frequent FreeBSD user, "FreeBSD/macOS" is not really a thing. There is historical shared code but they are different beasts. Sometimes there is substantial porting involved to get things from one to the other and they are not really the same entity. Additionally, the BSD pieces of macOS are frequently out of date and a hodgepodge of components.
Personally, I have very frequently had the experience that Unixy stuff that "just works" on *BSD or Linux does not work on Mac straight away, or breaks with a new OS release, etc. It takes effort for the homebrew folks or the macports folks or whatever to keep stuff working.
The way you've substituted "BSD" for macOS really doesn't make sense. Yes, there is BSD code in MacOS, quite a bit of it in fact. But they're not the same thing.