Hmmm, I guess that could be a tricky one to solve because it could be dynamic in what's considered "incorrectly". That might have to be looked at as an issue. Like a programming syntax error you might say.
I say that because where would you know to split and start a new? Especially because x amount of aliases can follow the host name. So if they are on the same line, they could all be considered aliases.
Aliases and Hostnames can be alpha-numeric as well as a dash and period, while IPs can only be numerical and a period. The reason I point this out is because since all the allowed characters of an IP are allowed in an Alias or Hostname, you wouldn't know when you got to a new IP.
It's probably why the standard is one per line, because when the file is parsed (or interpreted) by the system, they would run into this same issue, with only the return line being the delimiter as to a new IP.