https://www.zabbix.com/documentation/6.0/en/manual/config/items/itemtypes/zabbix_agent

Existing:
file_regexp - absolute path to file and the file name described by a regular expression. Note that only the file name is a regular expression

Comments on existing wording:
Perhaps due to past experience, and because the details were not explictly spelled out, I assumed that the regex must completely describe the filename pattern. ie I assumed the regex was anchored with ^ and $. And that if you wanted to match a word in the middle of the filename, you'd need to use a regex of:

.*some_word.*

Suggested:
file_regexp - absolute path to file and the file name described by a regular expression. Note that only the file name is a regular expression, and the regex need not match the entire filename. (e.g. regex of "abc" will match a logfile name of "prefix_abc_suffix.txt".)