I don't know if this is related to the changed made today (or recently) to Cloud Console, but I noticed that deleted (not just disabled) App Engine projects are not really, and can be accessed easily.
This causes some Server Errors here and there, and some other errors occasionally, as below, but works.
Project ID: {{project.assignedIdForDisplay}} Project Number: {{project.numericProjectId}}
Estimated charges this month: {{projectDetailCtrl.charges|panCurrencyByCode:projectDetailCtrl.chargesCurrency}}
I deleted (in Cloud Console) some "deleted" apps I still remembered. Maybe Google can list all "deleted" apps in the projects overview, so that they can be deleted properly(?) now.
I only noticed this because Cloud Console lists a billing account for an app I had "deleted" 1+ years ago. (It did not do so until today, or perhaps recently.) It would not let me close the billing account, because it still had a project associated with it. So to disable billing on the "deleted" account I had to figure out how to access it. (I'm sure I disabled billing before I deleted the app back then, but anyway.)
The old billing account cannot be deleted, only closed. I have "deleted" it from Google Wallet a year or so ago.