They were different circumstances though weren't they, the club wanted to give Nuno a send off for example. Also the last game of the season was a dead rubber last season, i'm not sure City would be too happy by that announcement (for all the difference it would make), and announcing Lopetegui before he has formally announced he is leaving may damage him too.
I think/hope that we have tapped up Lopetegui and that this season was all part of a medium/long term plan to "wait" for him (again). It would explain appointing Lage, the small amount of cash he was given and how little we have heard from the club generally and of course that JL is one of Mendes's clients.
Obviously this theory is more hope than expectation, especially as there hasn't even been a whisper of him joining us in the press.