I can't really help you other than to say I understand your frustration. Plant labels, nursery descriptions, and online descriptions can be wildly different. One of my local nurseries told me that a lot of plant growers will use a 10-year size on their labels, even if the plant will grow larger. So maybe that size is a 10-year size?

Crapemyrtles are easily maintained well below their maximum potential height. Personally, I think they are more attractive, and certainly more compact, if cut back every year. Your variety is said to top out at 20 to 25 ft. I wouldn't worry about it.

Trees don't top out until they die or become senescent. Sometimes they just slow way down. Even the tallest redwoods make new growth every year. Some of these forest giants don't grow beyond their ability to transport water by dying back and starting over. Others grow very slowly.

Annual hard pruning of crape myrtles has been called crape murder.

Annual hard pruning of crape myrtles has been called crape murder.

bboy, I hate pollarding. I bought a house with pollarded silver maples which are all rotting; trimming isn't enough to solve the problem, so I'm looking at removal and replacement.

However, the crape myrtles I'm familiar with all seem to bloom much more profusely when they've been pollarded. so my impression is that crape myrtles are more tolerant of severe pruning than other types of trees. [They're not my crape myrtles -- just some I see around town and where my parents live.]

Few plants are more slovenly than a crapemyrtle allowed to run wild. The bonehead behind me lets his go, and some of the branches of the same tree are a good 15 ft. apart, a sprawling mess. I suppose some ideological gratification may be derived from refusing to intervene in the natural order.