Just a quick question, what's the difference between end-on-ends and nested tickets?

home-aaa Jan
aaa-home Apr

with 2nd ticket as:

aaa-xyz Feb
xyz-aaa Mar

If no stay restrictions (say both are minimum Sat night and maximum 4 months or something) are circumvented, and the rules say "end-on-end permitted," is this allowed? I'm not sure if this would be any different than what sjunkerg posted originally, though.