In the RFC 2782 for SRV record type we can read:
The format of the SRV RR Here is the format of the SRV RR, whose DNS type code is 33: _Service._Proto.Name TTL Class SRV Priority Weight Port Target (There is an example near the end of this document.) Service The symbolic name of the desired service, as defined in Assigned Numbers [STD 2] or locally. An underscore (_) is prepended to the service identifier to avoid collisions with DNS labels that occur in nature. Some widely used services, notably POP, don't have a single universal name. If Assigned Numbers names the service indicated, that name is the only name which is legal for SRV lookups. The Service is case insensitive. Proto The symbolic name of the desired protocol, with an underscore (_) prepended to prevent collisions with DNS labels that occur in nature. _TCP and _UDP are at present the most useful values for this field, though any name defined by Assigned Numbers or locally may be used (as for Service). The Proto is case insensitive. Name The domain this RR refers to. The SRV RR is unique in that the name one searches for is not this name; the example near the end shows this clearly.
On the other hand in the RFC 6763 for DNS-Based Service Discovery they are using SRV record in such format:
Instance._Service._Proto.Name TTL Class SRV Priority Weight Port Target
Instance may contain almost all characters:
It MUST NOT contain ASCII control characters (byte values 0x00-0x1F and 0x7F) [RFC20] but otherwise is allowed to contain any characters, without restriction, including spaces, uppercase, lowercase, punctuation -- including dots -- accented characters, non-Roman text, and anything else that may be represented using Net-Unicode.
As an example we can get such record from dns-sd.org:
$ dig +noall +answer SRV "Service\032Discovery._http._tcp.dns-sd.org." Service\032Discovery._http._tcp.dns-sd.org. 60 IN SRV 0 0 80 dns-sd.org.
So my question is: does this SRV record format valid accordingly to RFC 2782? And if it is valid why, for example, cloudflare doesn't allow to add such record?