This is exactly what I do. I check that log multiple times per week. I just wish there was a way to filter by field name. Unfortunately, when someone posted that suggestion it was closed to lack of interest.
We saw this same issue for some time and gave up on Xenforo fixing it. We ask that new users insert certain details inside of profile areas so blocking profile editing wasn't an option for our site. We have found that the signup abuse detection and blocking created by Xon has helped a MASSIVE amount in stopping this issue, and we honestly don't see any Spam in these fields anymore......
I do the same. Caught quite a number of them this way.
I also have this spam phrase added to Spam Management that flags external links. I’ve set it for the first 5 posts of a new member. Works like a charm. Posts caught in the filter need manual approval.
One thing that this spam phrase is especially great for is detecting external links hidden in a period or comma. Apparently this is done for the crawling robots to pick up the link. So it’s like a spammer’s SEO tool.