All recipe calculators provide 0 bitterness from flameout (no hopstand) additions.
If I make my flameout addition, carry my kettle into the house, put the chiller in the kettle, and begin cooling within probably 2-3 minutes is any extracted bitterness pretty much negligible? For some reason, I got in the habit of doing 5 min hop additions because I didn’t trust a flameout addition as contributing 0 IBUs.
Negligible. Since you use a chiller, the wort is cooling quickly enough to extract negligible bitterness from a traditional flameout addition. If you addded a few oz @ flameout and steeped for 30 mins, different story. No worries.
If you’re concerned about it an alternative might be to add your flameout addition after you get it in the house. Put it in when you put the chiller in. Try it both ways with the same beer and see if you notice a difference.