Stable ABI and compatibility in each line ... and when you want new/more features - you upgrade to newer branch. Newer branch can also have some features removed like some old telnetd(8) or things like that - if for some reason you use/implemented them and still need them - you should stick to your currently used line (like 12.x) and with update from 12.3 to 12.4 these features will still be there for you.
There are also compat packages in pkg(8) repository - which you can use to have FreeBSD 12.x compatibility on FreeBSD 13.x for example. Thanks to the you do not need to recompile/reinstall your packages after upgrade from 12.x to 13.x for example:
Is this model better then LTS model? Its quite similar I would say. You have LTS with incremental updates or you have for example FreeBSD 12.x with security patches and 'major' upgrades with 12.1, then 12.2 etc.
The better thing in the FreeBSD world is that pkg(8) packages are ALWAYS up to date (or upstream) while the FreeBSD base system (12.x or 13.x) remains at what it is. This way you can stay on your prefered supported FreeBSD version and still have latest software with pkg(8). This is simply not possible on Ubnutu LTS or RHEL systems where packages are outdated and old very quickly.
Just a quick comment from a developer. One thing I love about Ubuntu is ease of installation and support for non-free firmware. Yes, I'm a horrible person for using non-free firmware. But I dislike how ancient packages in Ubuntu-LTR tend to be. After playing with Debian/Unstable and Debian/Testing, I moved back to Ubuntu-LTR, but now do all my development in a VMs with a recent version of FreeBSD or stock Debian (but mostly FreeBSD.)
I do almost exclusively server development, so I don't know if this would work well if you were developing OpenGL or Vulkan desktop apps, so your mileage may vary. (Or maybe someone can tell me OpenGL or Vulkan support across a VM boundary isn't as dramatic as I am assuming it is.)
There are also compat packages in pkg(8) repository - which you can use to have FreeBSD 12.x compatibility on FreeBSD 13.x for example. Thanks to the you do not need to recompile/reinstall your packages after upgrade from 12.x to 13.x for example:
Is this model better then LTS model? Its quite similar I would say. You have LTS with incremental updates or you have for example FreeBSD 12.x with security patches and 'major' upgrades with 12.1, then 12.2 etc.The better thing in the FreeBSD world is that pkg(8) packages are ALWAYS up to date (or upstream) while the FreeBSD base system (12.x or 13.x) remains at what it is. This way you can stay on your prefered supported FreeBSD version and still have latest software with pkg(8). This is simply not possible on Ubnutu LTS or RHEL systems where packages are outdated and old very quickly.
Hope that helps.