5 - 6 minute headways at that time on a Sunday morning is freaking excellent.
Maybe it'll just be like that for opening day, assuming that this schedule is for opening day next Sunday when the system will be overwhelmed?
As far as I was aware, in general, it will mostly have 4 min headways during the morning and afternoon peaks during the week, 7 minutes during the day off-peak and then 10 minutes after about 10.00 pm at night.
Weekends will be 7 minutes I think.