Hi,
no, that is not a problem at all - it simply means that the IP address of the DNS over TLS resolver you are using has no PTR set in DNS. For mail servers in particular, it is crucial to have these set properly, but other internet services rarely depend on a proper PTR configuration (and a matching A/AAAA DNS record).
“Status: OK” is the crucial information for being able to properly use a DNS resolver. 
Thanks, and best regards,
Peter Müller