I'd poke around and see if the roots are still developing, I've had one eaten by root pests and eventually the stem just fell over. On the other hand, the sour bubbling crack I just harvested did literally nothing for nearly 30 days. It was a little bigger than your sprout but she was at 2nd node for 2 and half weeks then as I was going to give up on her she decided, ok... No it's time to grow.
So finicky, well put Ultradan. You never know until you've tried the strain, but once you find the autos you like and that veg for 5 or 6 weeks then autos become a great addition to the cycle.
I think I'm going the same perpetual route as you Dirt. My plan is to focus on photoperiods veg and flower, but to throw in some autos if there's any room. I'm a huge fan of autos, but some can definitely be a waste of time and space. All those mini Me's are designed/created for Sog setups where you can grow 30 in a space I'd grow 9. Use one gallon pots and cram the tent full. 9 weeks later you got a decent harvest. But doing them Willy nilly, picking cool strains has got me in supply chain pickle a few times. It really helps to know your strain.
Goodluck to you for that sprout, we'll be watching...
KiG
cheers