Date of last change of an InnoDB table structure
I would say yes because any ALTER TABLE must change the timestamp of the last write to .frm.

To pull the UNIXTIME out, you would do this

ls -l --time-style=+"%s" mysql/data/mydb/mytable.frm | awk '{print $6}'


or to get the date time

ls -l --time-style=+"%Y-%m-%d %H:%M:%S" mysql/data/mydb/mytable.frm | awk '{print $6,$7}'


MySQL does provide an UPDATE_TIME column, but that's for changes to data or indexes.