Wendy, welcome to ATP.
Yes, always plant your tomatoes deep. The stem that is now underground will put out new roots. The stronger a root system the plant has the more it can grow and the more it can set fruit.
On tall leggy plants you can carry this one step further by laying the tomato plant on it's side horizontal in a shallow ditch. Gently bend the end upwards and fill in will soil. Not to worry if the top is not absolutely straight. You can straighten it as it grows. This method makes lanky weak growing plants strong as again the plant makes lots of roots along the buried part of the stem.
It does not affect the timing of fruit production one way or another but I do believe you end up with more fruit per plant in the long run. And not to worry that your new plants now look shorter because they are deeper. The plant is really still the same height.
Ideally you want to pinch off those bottom leaves that are on the stem that you will have underground. But if you forget to do this, don't worry as the plants will manage just fine.
I always plant my tomato plants as deeply as I can. It makes them thrive.
And I also am a firm believer in mulching those baby plants as soon as you get them planted to stop any soil borne diseases from splashing up on the tomato leaves. Cut off any leaves touching the soil even if you don't mulch. You want to keep your tomato plants as healthy as possible and keep those fungal diseases away as much as possible.
