Now a days most of the infant carry seats are rated for up to 35pounds and a pretty high weight limit. They work until age 2, on average sometimes even age 3. Not sure if that seat was, but most are fine to keep using. There legs are perfectly safe rear facing even if very squished. Research data shows there is very, very minimal risk of ever injuring the legs in a crash.

I would think (hope) most families stop carrying the kid in them long before then though. After the kid is past the newborn stage the seat can stay in the car and be used like any other rear facing car seat.