Seedlings dont get leggy from being transplanted into pots - they get leggy if they dont have enough light, (which is why they might be reaching for it). My tomato seedlings are wider than they are tall, and they have lived in pots all their short life (5 weeks)

It sounds like he might be making excuses for leggy plants. If they are really leggy you can deep plant them when they go in the ground. Tomatoes will form additional roots all along the stems,and you will end up with stronger plants.

Dont over do it with the fert right now wait until they are planted.

I agree with the above. Legginess has nothing to do with pots. It is caused by insufficient light while young and growing in the artificial environment of indoors. That problem is eliminated once they are planted outside - unless they are planted in the shade.

Excessive temps for indoor young seedlings can also contribute to legginess but light is the key. And yes, as mandolls implied above, it is totally possible to provide sufficient light, even indoors, and avoid leggy transplants. Many of us do it. :)

Dave