You are predicating that shape is required for interaction. What was said before was that the soul does not have physical form. There is also spatial form, which is not physical shape. We read that St Thomas Aquinas accepted St. Augustine’s view and explained that the soul is completely present in each part of the body just as in a specific sense whiteness is completely present in each part of the surface of a blank sheet of paper. The whole soul is in each part of the body by totality of perfection and of essence.
Summa theologica, part 1, question 76, art. 8
Since, however, the soul has not quantitative totality, neither essentially, nor accidentally, as we have seen; it is enough to say that the whole soul is in each part of the body, by totality of perfection and of essence, but not by totality of power. For it is not in each part of the body, with regard to each of its powers; but with regard to sight, it is in the eye; and with regard to hearing, it is in the ear; and so forth. We must observe, however, that since the soul requires variety of parts, its relation to the whole is not the same as its relation to the parts; for to the whole it is compared primarily and essentially, as to its proper and proportionate perfectible; but to the parts, secondarily, inasmuch as they are ordained to the whole.
newadvent.org/summa/1076.htm#article8