SoftDescriptors
Soft or dynamic descriptors allow merchants to supply information with specific payments that is used to populate customer statements.
By default descriptor information is configured for each merchant but if a particular merchant requires the support of soft descriptors, for example an aggregator that needs to refer to individual sub merchants, this can be supported.
Card schemes have certain restrictions on the number of characters supported and on the content of the descriptor data and not all acquirers/processors support soft descriptors. Please discuss with your account manager if you wish to use thisservice.
alpha.pwstaging.com.au/docs/alphahpp#softdescriptors-
So they are just dynamic statement descriptors.