The statement is correct: they would have difficulty making out shapes.
David Hubel and Torsten Wiesel did a series of experiments in the sixties in which they showed that there is a critical period shortly after birth during which the brain needs input from the eye in order to become organized in such a manner that a person can see. They got the Nobel Prize for Physiology or Medicine for this in 1981.
From the Nobel Prize website:
Hubel and Wiesel in their investigations were also able to show that
the ability of the cortical cells to interpret the code of the impulse
message from the retina develops early during a period directly after
birth. A prerequisite for this development to take place is that the
eye is subjected to visual experiences. If during this period one eye
is sutured even for a few days, this can result in permanently
impaired vision because the capacity of the brain to interpret the
picture has not developed normally.
A more detailed description of these experiments can be found here
As to what kind of sensations a previously blind person would have, if their eyes suddenly began to work, I don't know. The cells that Hubel and Wiesel describe, encode information about orientation. Perhaps it is true that seeing color would be possible.