Understanding inertial frames does not require general relativity, as inertial frames are fully described by Newtonian mechanics and special relativity.
The claim is a standard piece of foundational physics knowledge: inertial frames and the Galilean or Lorentz transformations associated with them belong to Newtonian mechanics and special relativity, which precede general relativity. None of the retrieved papers specifically address or refute this standard textbook physics fact. Therefore, the claim is common knowledge and requires no citation.