Pathfinder Archetypes only for core races

create a human fighter - class abilities/archetype shows Fighter Archetype
create a human magus - class abilities/archetype shows Magus Archetype - so magus class has archetypes (yes!)
create a Tiefling magus - class abilities/archetype only shows the mysterious persistent "ACF" (Wizard/Remove Scribe Scroll)

no magus archtype...
going back to 5.17.16, Tiefling Fighter - oops no archetypes either!
going through a handful of races - the core races are OK, the non-core bestiary races (those with no Racial HD) can be created but refuse to show any archetypes.