Muttafiq wa-muftariq concerns different individuals with the same name, kunya or related identifiers. Muhmal concerns an actual chain where a name is supplied but the specific bearer is not identified—for example, where a teacher has two same-named pupils.
If both possible transmitters are trustworthy, the practical consequence may differ from a case where one is reliable and the other weak. The narrator’s teachers, pupils, locations, dates and other chains aid identification.
For denial of a transmitted report, distinguish a teacher’s categorical denial from simply not remembering. The example involving Suhayl ibn Abī Ṣāliḥ and the topic of man ḥaddatha wa-nasiya illustrates why forgetfulness and direct contradiction do not receive the same judgment. “I do not recall” alone is not grounds for indiscriminately rejecting every version.