We need to distinguish between new means of compliance proposed by competent authorities and those by organisations.
If the competent authority proposes a means of compliance for use by organisations, it is most likely an AltMoC. The reason is that the AltMoC might express expectations that need to be met by the regulated entities so as to establish rule compliance.
Conversely, if the competent authority establishes a means of compliance for itself (i.e. to Part-ARx) or an organisation proposes a means of compliance, it might be a description of an organisational process or standard operating procedure, implementing for example a prescriptive implementing rule. Process descriptions or detailed standard operating procedures reflecting the work of an individual entity are not per se AltMoC.
Nevertheless, the above can only be a general guideline. Organisations and competent authorities may need to evaluate each case to establish if a means of compliance is an AltMoC.