First grow questions

Ok so I'm on my first grow and although I plan on doing photo plants mainly this first grow is with autos due to time constraints.

4 Seeds went into water on the 10th I put them in paper towels on the 11th and into 2" Rockwool cubes on the 12th all 4 have sprouted through the rockwool and are doing pretty good. I have one that is lacking a little. It had a hard time shaking the seed hull I had to help it but I'm not sure if it's gonna make it. Watered them for the first time today since going into rockwool so about 3 days. There going to go into 3 gallon smart pots with FFOF/Perlite mix but my question is when should I be looking to move them to the pots?

Once roots show at the bottom?

When the seed hull reaches past the cube hole is the minimum. Or you can wait for some reason till there's a tap root out the bottom.

I sprout seeds in grodan cubes. Out of habit I wait till there's a tap root breaking the bottom surface of the cube before soil.....and I have no idea why.

That's what I was planning just wanted to make sure that was right.