Is it always stress related, I know cuttings I take from a mature plant will flower after one or two leaf nodes. I do pull them off, so they can focus on growing roots.

Ok thanks, I just find it strange why they are trying to flower.

it's because store bought plants are usually in the pot too long and/or not receiving proper care, so the plants have a special way of sending signals to start producing/seeds before they die to avoid becoming extinct ;)

see this for the technical side of what i mean:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4091191/

Nothing strange about it. A plant that is stressed tries to put out seeds asap.

To me , it depends on the age and size of the plant too.

In average a tomato will produce first ripe fruit in ~ 100 days ( +/- 10 )

My first batch ( sowed Jan 19, planted 3 days ago ) most are flowering. They are already 65 days old and should have ripe fruits 35 to 45 days from now. That has nothing to do with being stressed. I will just let them do their own thing. BTW: They are 14 to 18" tall with good size stem.