Someone in relation to the CRUX project emailed me, after I published this post, with the following info:

Please check the contrib/yubikey-personalization package which contains an
udev rule which handles the permission problem.

Sure enough, there sat a file with 3 udev rules which addresses the permission issue. No need for the overblown/catch-all 69- and 70- rule files published on yubico.com.

Thank you, sir!