Yep, just autos being autos. I grow autos, and out of 17 plants, I've had 4 that have been pretty lacklustre and initiated flower around day 15. Also had some absolute killers that have pulled close to half a pound with three or four weeks veg.
If you are banking on yield and can only grow one or two plants I'd consider photos tbh, but of you like the challenge and the luck of the draw, continue on...I like the torture and suspense so I have haha.
The issue with most autos is that they usually already use already convoluted hybrid genetics that have a large pheno pool and once you add ruderalis and multiple back crosses to stabilise the traits, you have a very large pool of phenotypic variety. That can be fun at the same time, and you can get some unique traits, but can also be a massive hindrance if you are relying on a single, or two plants.
This was my last amnesia auto in a 3x3.
This was a purple Passion that was popped under the same light, in the same medium with the same feed which went into flower around day 17. The amnesia got around 35 days veg. That's a little 8" pot, and the plant totalled 40cm lol. The amnesia for a comparison was in a 14" square pot.
Sometimes you can give them the best life and they'll still give up, other times you'll treat them like dirt and they will prosper. Some like the lottery, some can't stand it.