IF Mobility Rule - what counts, the residency or the work contract?

If you take a general case where a researcher holds an employment contract in country A, but goes for 6 months to country B (keeping the same employment contract i.e. employer), the EC services will not remove this period of 6 months out of the calculation with respect to the mobility rule regarding country A, due to the fact that the researcher was physically present in country B. The employer will always be considered. This is also why REA asks the researcher during the eligibility check, to confirm who was the employer during this 12-month period before the call deadline.