What a coincidence

Not really

Wow it's almost like they're designed to support a human body properly.

That “gamer chair” like many, is designed after (or for higher end models actually) a seat for performance or racing cars. The boosters are designed to hold a human body in place, especially at the shoulders and hips, against high G forces so that a driver can remain in control. Leading companies like Recaro pioneered the field, as they supply seating for Space shuttles, aircraft, Public transport, etc (Recaro also makes high end baby seats too!) and it makes sense considering that to a baby, with its poor motor control and muscle strength- normal gravity or just the weak forces of “around town” driving are “high G.” But both baby and performance car seats also have additional crash protection over a more “standard” design.