I do have it set to log All Traffic, with a combination of WP Approve User installed (so registrations aren’t a direct security risk) and WPForo which is where the registrations all come from.
However, while I was looking at a batch of new registrations that came in this morning I saw that there _was_ activity on the signing page that Wordfence did track, I just wasn’t seeing what almost all my registrations seem to do (attempt to log in immediately) which stands out more in the log. So it appears to be the behavior of the bots and my not noticing it before rather than a Wordfence issue. Thanks for the reply and sorry for wasting time with what looks like a PEBKAC issue.