The Miller effect is real and there are references available on the internet, such as the youtube video I included in the slide I attached. Op-amp manufacturers seem to have found ways to suppress this effect. As you know, an op-amp is expected to be much more complex than what can be covered by just a single device.
But I am not an expert in op-amps; some of your questions require someone else to answer. Since Mike confirmed that this is an intended characteristic, I trust his word as he is an expert.
I saw TI and AD opamp model with this characteristic, and I posted my observation in this reply.
Rail-to-Rail Output OpAmp (Ã-Device RROPAMP) Instance Param - QSPICE - Qorvo Tech Forum
There is a discussion about quiescent current in this forum in last week.
@bordodynov add a negative resistor (-10kohms) to compensate that currently
@tobalt Have you contact Mike in clarify what is happening in RRopAmp quiescent supply current?
Quiescent supply current of Opamp RROPAMP - QSPICE - Qorvo Tech Forum