Thanks to all for providing the answer and details!
The reason for asking this, like always, due to historical reasons :)
Before migrating our Docker registry to Nexus, we used Docker's private registry sofwate, that allows anonymous push and as you may have guessed, is what we had, as a pre-req befire migrating to Nexus we've done quite a bit of overhaul around or procedures and CI code to make sure authenitcation is used, but we keep hitting various corner cases where it was not fixed or it's somewhat complicated to fix...
I realize this is not the best practice approach, but we were looking to get our teams unstuck as this was holding back releases...
@Joe - Thanks for the workaround :)
So, here is our story... I realize that this approach is not ideal/best practices, but in real world - such situations as above is common and I think flexibility in our tools is very important to be able to support the demand for high-velocity in development processes today, so giving the option doesn't necessarily means you have to endorse it, it may come with a warning - but still be there to solve an immediate problem and get the ball rolling again, especially as Joe has explained - it is possible!
Just my 2 cents ;)
Thanks for listening (i.e. reading)
Regards,
Danny