Wrong. The sentence here is:
“...at least 8 years old or 4 feet, 9 inches tall...”
1 is supposed to parallel the phrase “at least” to BOTH of the descriptions. It’s parallelism.
‘at least 8yo OR AT LEAST 4’9”’.
Besides, I think most people know that 1 PROGRESSES not only from 7 to 8 to 9, but from 4’8” to 4’9” to 5’0”, etc. Generally, no human regresses in age/size!
Exactly. Once the child is 8 years old, the "or" means the conditions have been met. A 4'1" 9-year-old would not have to sit in a booster seat.