I had that very same concern, too, with my grow now, two strains of autos. My plants are about two weeks behind yours. I thought the same with my Blueberry X Big Bud as it seemed to not be flowering. It has finally started. I kept wondering if I got photos instead.
Looking at your two strains GSC says 8 weeks. One thing I know about the GSC-EXT auto I got here, have not grown yet but a friend (gave some seeds to) did this summer in his garden, I was surprised that it took more like 15 weeks start to finish for him. So not sure there what is going on. He had never grown autos, been growing for about 40 years or more, so not sure if he was just used to having a plant go all summer long and harvested late or what. He lives about 500 miles away so never got to see the grow in person.
Gelato auto says 10 weeks finish. My Blueberry x Big Bud is just now starting to flower and it was a 10-12 week finish.
The thing I have read on how many weeks a plant flowers or finishes out is that these figures are geared more toward commercial growers and it can fall a bit short of what a realistic home grower can finish one out. Not sure on the validity of that but makes sense to me. The times to finish are just estimates.
I would say be patient and see what next couple of weeks brings. Do they have small pre-flowers yet?