The thinking is for when a pool is doing some kind of maintenance (either to update their code/settings, or reboot the machine). It's "good manners" for the pool to notify the miner in ADVANCE, that way they can move to a fallback pool/server before suddenly losing connection. A "retry/wait" time should also be included in the restart method, so the miner knows how long it should wait before trying to reconnect.
Ok, I can add it into the specs, but most likely I won't implement it in my code, just because all these fancy features are making things complicated, without providing any materialized benefit.
For example the twisted framework in proxy is solving reconnections automatically for me, in exponential back-off (it will reconnect and if it fail, next retry will be after longer time). I think it's quite fine behaviour and forcing it to strictly follow the wait interval provided by the server will just require some hacks.