They might sound minor but in practice they violate assumptions that are really crucial for implementations. Everyone who deals with addresses must make decisions about how and what to do in face of these quirks.

Another example is the zone identifier string. So how do you store them efficiently in memory or a db? Golang did a really clever thing with netip but the implementation was not easy. Oh well maybe we can always ignore and strip it? Maybe, depends on the use case.

The point is going from exactly 32 bit to 128 bit + sometimes maybe a variable length string (max length, encoding, allowed chars?) is not a small change for something so important and ubiquitous as ip.