It seems, that the "options" parameter is missing in the log item description in Russian documentation:
https://www.zabbix.com/documentation/5.0/ru/manual/config/items/itemtypes/zabbix_agent
And also here:
https://www.zabbix.com/documentation/current/ru/manual/config/items/itemtypes/log_items
In English version the item has this description:

log[file,<regexp>,<encoding>,<maxlines>,<mode>,<output>,<maxdelay>,<options>] 

With the <options> parameter described as:

options (since version 4.4.7) - additional options:
mtime-noreread - non-unique records, reread only if the file size changes (ignore modification time change). (This parameter is deprecated since 5.0.2, because now mtime is ignored. Before 5.0.2 the file would be reread by default if either the modification time or file size changed.)

But in Russian version it's only this:

log[файл,<регулярное выражение>,<кодировка>,<макс. кол-во строк>,<режим>,<вывод>,<максзадержка>]