So are the BSD tools by some definition of "behind". Another way to look at this is to say that GNU tools as typically seen in modern Linux are bloated (I know, Linux and "bloat" are kind of a meme, but it is generically true for the most part when it comes to the command line utilities feature creep over the years, so it's a useful and descriptive word).
I have to work with old machines and legacy operating systems quite a bit in my day to day and I always am going to prefer something lighter and with less ways to shoot myself in the foot w.r.t. POSIX compliance. MacOS is Unix certified so I appreciate them being somewhat reserved in the features they add on top of POSIX.
Modern GNU userland utils are nice and fun but if you are looking for compatibility it's best not to use them. Consequently, the MacOS situation doesn't bother me especially given you can install more up to date tools if you want. I think keeping the defaults older and more compatible is a good thing.
There is poor cross-UNIX compatibility if you're doing anything complicated, anyway. I maintained a large test suite for about a year that was written in POSIX sh and targeted Linux, macos, {Free,Open,Net}BSD. It wasn't fun because every program behaved in slightly different ways, half of them undocumented (for example, I remember having lots of pain with how different versions of tail handled SIGPIPE).
In the end it was was easier to rewrite in Perl than to keep maintaining that thing, struggling for hours to find ways of implementing every little bit of functionality that worked reliably on every OS. You'd add or fix something, and the tests would break on FreeBSD. You would fix it there and it would stop working on NetBSD. And so it goes.
I prefer a lot of the BSD variants of the typical POSIX tools (i.e. bsdtar vs GNU tar, ksh or similar instead of bash, etc etc). Usually because they add less extensions on top of what is required by POSIX, but are still easily acquired in a modern Linux distribution. I mostly just alias them.
If I write a script using BSD esque tools I can be reasonably sure they will work on any Unix-like, whereas if I write/test my script on a machine using GNU utils, I'm fairly likely to accidentally use a GNU extension that would cause the script to fail on an older Unix-like OS. For instance, I do a lot of work migrating code off of AIX,and I need the scripts I develop to work on AIX when I'm gathering environment information from customers. I can't just assume they will have a ~2020+ implementation of Unix userland tools with all the GNU extensions and nice features. Sometimes the machines have been sitting quietly in the back of a data center not being updated for quite a while and will have more "90s style" of Unix tools.
I have to work with old machines and legacy operating systems quite a bit in my day to day and I always am going to prefer something lighter and with less ways to shoot myself in the foot w.r.t. POSIX compliance. MacOS is Unix certified so I appreciate them being somewhat reserved in the features they add on top of POSIX.
Modern GNU userland utils are nice and fun but if you are looking for compatibility it's best not to use them. Consequently, the MacOS situation doesn't bother me especially given you can install more up to date tools if you want. I think keeping the defaults older and more compatible is a good thing.