neo-mat/arcemu — comment on commit 0488ec26c6efd808c24b64ce2fceb1a9e37dddef
File: src/arcemu-world/Spell.cpp line 1491
By neo-mat:

Well RemoveAurasByInterruptFlagButSkip has custom checks for spells, to remove aura only on specific spell cast. For example Hot Streak proc applies aura to you and that aura should be removed only after casting Pyroblast, if we would cast Fireball aura should stay till it expires or Pyroblast will be casted. And such auras have AURA_INTERRUPT_ON_CAST_SPELL, that means remove only on spell cast. But AURA_INTERRUPT_ON_CAST means to remove aura by any cast, e.g. casting Mortal Strike or Fireball, it affects any cast, so such auras with INTERRUPT_ON_CAST should be removed because they are not designed to be removed only after cast of some specific spell.