While the American Academy of Pediatrics now recommends keeping a child rear-facing until age 2, we opted with both of our kids (ages 4 and 2) to move them forward at 1 year.
In our son's case, it wasn't the recommendation at the time.
In our daughter's case, it was, but she was SO scrunched because of how tall she is for her age.
Luckily we made it through the year without any accidents to test whether we'd made the right decision.
I understand their logic based upon their muscle strength and ability to be injured in an accident. It became an issue of practicality for us, and we felt comfortable making that choice in both cases.
Good luck.