Hi!
Unfortunately this change isn't being driven by us, it is driven by Google - see the announcement for more info
The exact timings depend on Google.
Google really don't like users not using their own client id. I tried to persuade them that they know who the user is anyway so why make this change, but you can guess how well that conversation went!
We would automate the client id creation if we could but unfortunately Google still has no public API for creating standard OAuth 2.0 clients (Desktop/Web app type on the consent screen).
So I'm afraid we have been painted into this particular corner by Google 