With regard to variations in surname spelling, it is important to distinguish between, and identify, the variants and deviants of any given surname.
Surname Variant: phonetically similar surname spelling which is used by a family and/or consistently recorded in official documents, for at least several consecutive generations, including the present.
Surname Deviant: surname spelling which results from recorder unfamiliarity and/or recording/transcribing/indexing/coding error(s), and is not used by a family and/or consistently recorded in official documents, for at least several consecutive generations, including the present.
Official Document: document created and maintained by officials containing records of birth, adoption, marriage, divorce, death, residence, military service, land transaction or taxation, pension payment, or probate.
Because surname variants and deviants are discovered in the process of genealogical research, indicating deviant surnames in the "Other Last Names" field serves no constructive purpose.
When variant surnames occur, they should be indicated in the "Last Name at Birth" and/or "Current Last Name" fields.
So, I also prefer to limit the "Other Last Names" field to multiple marriage surnames.