Which is a house rule.
Not even a good one. Only in some special circumstances.
Characters in movies often reaact before the combat triggering action is resolved.
Usually advantage vs disadvantage simulates it corretly.
In one campaign I actually started using initiative on social encounters. I was DMing a campaign for a group of friends (I was not in the friend group) and one of them was playing a Barbarian who just talked over everyone and took over every social situation. To make matters worse he had a terrible Charisma and no social skill proficiencies and they had Bards and Rogues at that table with expertise in Charisma skills.
After talking about it and after some at the table complained it did not stop. So I just started using initiative, you only talk on your turn as your action or as a reaction to someone addressing you (and NPCs could do the same). So if you won initiative you said something (action), then the guy you said it to talked back to you (reaction), then you could reply to him (reaction), then it would move to the next person. It was very clunky but it fixed the problem.
A few discussions transitioned to combat and we just picked up from where we were in initiative.






