Hi sageib, welcome!
There are many approaches to getting earlier fruit, and one of them is to start them earlier, as you do, and pot them up decently to get them large before transplant. But the person I know who has practiced that (KarenO), would often have fruit as well as flowers on the plant before transplant time. Naturally those fruit that set before you put them out should be earlier than the "dtm" from the time of planting out, I would think.
Anyway you'll probably hear more about it from her.
I have a short and cold growing season here, but I don't have space for big pots indoors. My plants are flowering or close to it by 8 weeks and that's when I plant them, but I don't cull early blossoms as I want those early fruit. I've never seen them cause any harm with the varieties I've grown - if the plant doesn't want to set yet, they will drop the blossoms themselves, anyway. But most of them are happy enough as long as they get planted when the flowers start. And planting out at 8 weeks, I usually have lots of fruit set by 15 weeks - even some ripe ones on early varieties. So I'm wondering if you don't have flowers and fruit at 15 weeks? because if not, there is likely no benefit to the long time under lights, and maybe they are shutting down the fruit cycle until they get some root space.
This past year I had to hold my plants indoors (in beer cups) for an extra two weeks because of extreme cold weather. This definitely delayed them in setting up fruit, and it had a variable impact depending on the variety - some were really badly affected, others not so much.
So I think it depends on two things (1) how big of a pot do you have them in, and is it big enough for them to start setting fruit as if they were in the ground, and
(2) different varieties of tomato will respond differently to the treatment.