FieldType 'MULTIPLE_RECORD_LINKS' lacks relationship option (single vs. multiple foreign records)

[kaz875]

I am using the Block API and noticed that the FieldType 'MULTIPLE_RECORD_LINKS' doesn't provide information about the relationship option (whether it allows linking to only a single foreign record or multiple records). This information can be quite important to handle the foreign key field differently.

There's also not a 'SINGLE_RECORD_LINK' FieldType either (which would be more ideal actually).

Is that a known issue, or there's anywhere I can get that information through the Block API?