I was looking out how NMAP identifies DNS services. After determining that port 53 is open it issues a standard query TXT version.bind to find out if BIND is running on the domain port. Then, I saw that after NMAP received the response:
it issued a "Server Status Request" and received a "Server Status Request Response, Not implemented" and displayed port 53 as open but did not specify a version. What is a "Server Status Request" and why did NMAP not lable the port as running BIND considering that it received the version?