yes the wayfarer discussion discord has an infographic posted from way back where proximity block has been observed. actually the last comment i made was based on this infographic as well.
please note that these are observations by explorers participating in wayfarer, not announcements from niantic that this is how or why it works.
others have been reporting a general slowdown, too. i am not submitting enough these days to notice, but @niktero has reported that it feels like something has changed, at least in more rural areas. Significant delays in Aragon, Spain: Nominations stuck "In Voting" for months - #5 by niktero