Cole may be right. I'm sure there are some that start tall but have short internodes between stems and stay small, just like there are those that start small then take off after they put out a set of blossoms - but I think they are the exception.
On F2s & F3s of crosses with indeterminates, I sow lots of seed and cull heavily before the first true leaves show up. In those generations I plant them fairly densely and don't have the time/space to pot them all up to avoid missing the exception. Planted densely, the true micros end up not doing well because they get overshadowed and don't get the light and space they need to thrive. Mine are usually planted more densely than yours. Yours appear to have plenty of room for a while yet. As long as they don't interfere with each other, the longer you wait to cull, the more accurate you will be. That also pertains to when you plant them out or into their final pot. I give them more time as seedlings and also more time in their first pot than regular indeterminates. They stay much manageable and the extra time gives you more information to make your decisions.
It really depends on your situation. You'll eventually get callous and snip away with ease.....
