Unfortunately, no. I guess it is because Solaris 11.4 was originally going to be Solaris 12. It has a lot of new stuff and modifications compared to 11.3. I guess they wanted to optimize it for the newer SPARC processors (or get enterprises to update their old systems).
I don’t think Solaris gets much attention from either the blue or red side these days. Patched or not, I would keep a Solaris machine segmented off with my other retro crap and not use it for anything public-facing where it might be exposed to attack.