One good thing about IPv6 is that any reasonable allocation will be large enough to use sizable chunks as functional divisions.

A small company might have a /48. You don't have to be concerned about address space when you just go, ok, first bit is for security zones. Or first 2 bits. Or first 3 bits. Do you need more than 8 security zones?

(Also, ULAs¹ exist, and most people should use them, independent of a possible consideration to not roll out GUAs² in parallel as one would normally do.)

¹ Unique Local Address, fc..: and fd..:

² Global Unicast Address