Dear fellow hard core Sativa man
Yes, they will continue to veg.
In general, cannabis, especially Sativa will continue to veg when light hours is long. 13 hours is the limit. I feel safer at 15 hours. It is light hours and sun angle and not about temp and humidity. I put plants into flower at 36 degree C and 70 %RH.
My thoughts:
Jack Herer original strain can be slow to develop. People may blend in auto genes to make it more user friendly. This may make them flower easier.
What I would do is to get some light on them at night for a month. Doesn’t need to be strong. 20 W from 5 meters away will do the trick. Then the natural sun schedule should be long enough.
A little pistil at this stage is still okay. The young flower buds will turn into branches. And you will need to trim it off later. Left longer, bus will mature and growth will practically stop.
For insurance, you may want to snip off a side branch and clone it. Season is still early enough.