Do you know if this will affect the ability of Apple Mail to auto populate email addresses from prior correspondences?
For instance, if I start a new email and begin typing a name in the To: field, "Dan..."
A drop-down list of names that begin with Dan appears (and the associated email):
Dan A - dana@gmail
Danny Z - dannyz@gmail
None of these individuals are saved into my i/macOS Contacts app, so I assume this feature works based off of prior correspondences to these individuals. This is a convenient feature that I do not want to lose.
However, I too am having the problem you described: emails recently began to be added to my i/macOS Contacts, sometime even appearing as DanA@gmail, etc. I also found instances of duplicated contacts. I changed no settings myself, so I suspect that it must be related to an i/macOS update and/or a gmail setting.
Seems like a highly undesirable effect, so not sure why Apple/Google would impose it as the default setting (instead of an opt-in approach).