The free movement directive" (Article 10 of Directive 2004/38/EC)

Hi

I am British citizen, living in Ireland since December 2018. My parents live in United State. They have US Green Card. They hold Pakistani passport but permanently living in United States. Now I want them to come and live with me here in Dublin under the free movement directive.
I was advised by Embassy of Ireland over the email, I have to apply for short term visit visa to exercise "The free movement directive" (Article 10 of Directive 2004/38/EC) for my parents in America and once they are in IRELAND then they can apply for Residence card of a family member of a Union citizen and continue living with me permanently.
I applied for their visit visa last week. I received email from Embassy of Ireland in Washington stating that “This category of visa will have to be forwarded to Dublin for decision as they do not have delegated sanction in DC (USA) to do so”.
Initially I was told that it will take them three weeks to issue visitor visa to my parents in Ireland but now Embassy of Ireland is telling me that It can take up to 6 months if I want to apply under the directive or otherwise, they can issue visit visa in 3 weeks.
Now they are in possession of my parents passport. They can’t wait for 6 months. They have other travel arrangements as well.
Can we go for visit visa now and apply for Residence card of a family member of a Union citizen within three months of arriving in Ireland?