It's not very clear to me why in paragraph "Truncation matters" it is claimed that the strlen variant is necessarily better than the strlcpy variant. the strlcpy variant only scan the source and destination string once in the fast case (no reallocation needed), while the strlen variant needs to scan the source string at least twice. I guess in the common case you have to enlarge the destination a few times, then once it's big enough you don't have to enlarge it anymore and always hit the fast case, os it makes sense to optimize for that.

It might also be that in some programs with different access patterns that doesn't happen and it makes sense to optimize for the slow case, sure, but the author should acknowledge that variability instead of being adamant on what's better, even to the point of calling "schizo" the solution it doesn't understand. In my experience the pattern of optimizing the fast path makes a lot of sense.

BTW, the strlcpy/"schizo" variant could stand some improvement: realloc() already copies the part of the string within the original size of the buffer, so you can start copying at that point. Also, once you know that the destination is big enough to receive a full copy of the source you can use good old strcpy(). Cargo cult and random "linters"/"static checkers" will tell you shouldn't, but you know that it's a perfectly fine function to call once you've ensured that its prerequisites are satisfied.