Yeah, I guess we'd need to know the specifics. Looking at the carseats measurement page, 38" seems pretty common among the brands. Heck, Harmony has a 34" minimum for NBB mode
. I would think that the vast majority of booster ready kids would certainly be above 38". Of course, there's always be children with growth disorders, dwarfism, etc. that could be booster ready before the height minimum. But I think those cases would be very, very rare.
ETA: I see your little peanut is a short, little peanut! If it's for her--and only YOU can determine if she' ready for booster training or not--I'd stick to a booster with lower stated limits (Harmony is one, I know there's others), as long as she still gets a good fit.